by Debasis Samnata
The java.awt Package provides an integrated set of classes and interfaces that manages standard graphical user interface (GUI). It contains GUI components such as buttons, lists, menus, and text areas. In addition to these , it also includes containers such as windows, menu bars etc. and higher level components such as diolog boxes, check boxes, scroll bars etc. The AWT contains two more packages : java.awt.image and java.awt.peer. These two packages will be presented in Chapter 21 and Chapter 22 respectively. The various constituents in the java.awt package is listed below :
Classes Class BorderLayout Class MenuBar Class Button Class MenuComponent Class Canvas Class MenuItem Class CardLayout Class Panel Class CheckBox Class Point Class CheckBoxGroup Class Polygon Class CheckBoxMenuItem Class Rectangle Class Choice Class ScrollBar Class Color Class TextArea Class Component Class TextComponent Class Container Class TextField Class Dialog Class Toolkit Class Dimension Class Window Class Event Class FileDialog Interfaces Class FlowLayout Interface LayoutManager Class Font Interface MenuContainer Class FontMatrices Class Frame Errors Class Graphics Class AWTException Class GridBagConstraints Class AWTError Class GridBagLayout Class GridLayout Class Image Class Insets Class Label Class List Class MediaTracker Class Menu
A BorderLayout lays out a container to contain number of GUI element like buttons, labels, Grids texts etc. Following is the varopus methods in this class :
public class java.awt.BorderLayout extends java.lang.Object
implements java.awt.LayoutManager
{
// Constructors
public BorderLayout();
// Default constructor, constructs a new border layout.
public BorderLayout(int hgap, int vgap);
/* Creates a new border layout with the specified horizontal and vertical gaps. The horizontal and vertical gaps specify the space between the components.
*/
// Methods
public void addLayoutComponent(String name, Component comp);
public void layoutContainer(Container target);
public Dimension minimumLayoutSize(Container target);
public Dimension preferredLayoutSize(Container target);
public void removeLayoutComponent(Component comp);
public String toString();
}
Methods in this class are described in Table 4.1.
Table 4.1
This class creates a labeled button.
public class java.awt.Button extends java.awt.Component
{
// Constructors
public Button();
// Creates a button with no label.
public Button(String label);
// Creates a button with the indicated label.
// Methods
public void addNotify();
public String getLabel();
protected String paramString();
public void setLabel(String label);
}
Table 4.2
A Canvas component represents a blank rectangular area of the screen onto which the application can draw or from which the application can trap input events from the user. An application must subclass the Canvas class in order to get useful functionality such as creating a custom component. The paint method must be overridden in order to perform custom graphics on the canvas. The AWT sends the canvas all mouse, keyboard, and focus events that occur over it. The gotFocus, lostFocus, keyDown, keyUp, mouseEnter, mouseExit, mouseMove, mouseDrag, mouseDown, and mouseUp methods may be overridden in order to catch user events.
public class java.awt.Canvas extends java.awt.Component
{
// Constructors
public Canvas();
// Methods
public void addNotify();
public void paint(Graphics g);
}
Table 4.3
A layout manager for a container that contains several "cards". Only one card is visible at a time, allowing the application to flip through the cards. This class provides us to manage such cards.
public class java.awt.CardLayout extends java.lang.Object
implements java.awt.LayoutManager
{
// Constructors
public CardLayout();
// Default constructor, creates a new card layout.
public CardLayout(int hgap, int vgap);
/* Creates a new card layout with the specified horizontal and vertical gaps. The horizontal gaps are placed and the left and right edge. The vertical gaps are placed at the top and bottom edge.
*/
// Methods
public void addLayoutComponent(String name, Component comp);
public void first(Container target);
public void last(Container target);
public void layoutContainer(Container target);
public Dimension minimumLayoutSize(Container target);
public void next(Container target);
public Dimension preferredLayoutSize(Container target);
public void previous(Container target);
public void removeLayoutComponent(Component comp);
public void show(Container target, String name);
public String toString();
}
Table 4.4
A check box is a graphical component that has an "on" (true) and "off" (false) state. Clicking on the check box changes its state from "on" to "off" or from "off" to "on". When the check box is clicked, AWT sends an action event to the check box. This event's target is the check box, and its object is a Boolean giving the new state of the check box. An application should override the action method of the check box or of one of its containing windows in order to cause some action to occur. Optionally, several checkboxes can be grouped together into a CheckboxGroup. At most one button in a group can be in the "on" state at any given time. Pushing a check box to turn it "on" forces any other check box in the group that is "on" to become "off".
public class java.awt.Checkbox extends java.awt.Component
{
// Constructors
public Checkbox();
// Creates a check box with no label. The check box is set to "off" and is not part of any check box group.
public Checkbox(String label);
// Creates a check box with the specified label. The check box is set to "off" and is not part of any check box group.
public Checkbox(String label, CheckboxGroup group, boolean state);
// Creates a check box with the specified label, in the specified check box group, and set to the specified state.
// Methods
public void addNotify();
public CheckboxGroup getCheckboxGroup();
public String getLabel();
public boolean getState();
protected String paramString();
public void setCheckboxGroup(CheckboxGroup g);
public void setLabel(String label);
public void setState(boolean state);
}
Table
4.5
This class is used to group together a set of Checkbox buttons. Exactly one check box button in a CheckboxGroup can be in the "on" state at any given time. Pushing any button turns it "on" and forces any other button that is "on" to become "off". When a check box in a check box group is clicked, AWT sends an action event to that check box. This event's target is the check box, and its object is a value equal to Boolean.TRUE . No action event is sent to the check box (if any) that is turned off. An application should override the action method of the check box or of one of its parent containers in order to cause some action to occur.
public class java.awt.CheckboxGroup extends java.lang.Object
{
// Constructors
public CheckboxGroup();
// Default constructor, creates a new CheckboxGroup.
// Methods
public Checkbox getCurrent();
public void setCurrent(Checkbox box);
public String toString();
}
Table
4.6
This class represents a check box that can be included in a menu. Clicking on the check box in the menu changes its state from "on" to "off" or from "off" to "on". When a check box menu item is clicked, the AWT sends an action event to the check box menu item's containing frame. The event's target is the check box menu item, and its object is the string label of the check box.
public class java.awt.CheckboxMenuItem extends java.awt.MenuItem
{
// Constructors
public CheckboxMenuItem(String label);
// Creates a check box with the specified label. The check box is initially set to "off".
// Methods
public void addNotify();
public boolean getState();
public String paramString();
public void setState(boolean t);
}
Table 4.7
The Choice class presents a pop-up menu of choices. The current choice is displayed as the title of the menu. After any choice is made, AWT sends an action event to the choice menu. The event's target is the choice menu, and its object is the string label of the currently selected item. An application should override the action method of the choice menu or of one of its parent containers in order to cause some action to occur.
public class java.awt.Choice extends java.awt.Component
{
// Constructors
public Choice();
/* Creates a new choice menu. The menu initially has no items in it. By default, the first item added to the choice menu becomes the selected item, until a different selection is made by the user or by calling one of the select methods.
*/
// Methods
public void addItem(String item);
public void addNotify();
public int countItems();
public String getItem(int index);
public int getSelectedIndex();
public String getSelectedItem();
protected String paramString();
public void select(int pos);
public void select(String str);
}
Table 4.8
This class encapsulate colors using the RGB format. In this format, the red, blue, and green components of a color a each represented by an integer in the range 0-255. The value 0 indicates no contribution from this primary color. The value 255 indicates the maximum intensity of this color component.
public final class java.awt.Color extends java.lang.Object
{
// Member elements
public final static Color black;
public final static Color blue;
public final static Color cyan;
public final static Color darkGray;
public final static Color gray;
public final static Color green;
public final static Color lightGray;
public final static Color magenta;
public final static Color orange;
public final static Color pink;
public final static Color red;
public final static Color white;
public final static Color yellow;
// Constructors
public Color(float r, float g, float b);
/* Creates a color with the specified red, green, and blue values, where each of the values is in the range 0.0-1.0. The value 0.0 indicates no contribution from the primary color component. The value 1.0 indicates the maximum intensity of the primary color component. The actual color used in rendering depends on finding the best match given the color space available for a given output device.
*/
public Color(int rgb);
/* Creates a color with the the specified RGB value, where the red component is in bits 16-23 of the argument, the green component is in bits 8-15, of the argument, and the blue component is in bits 0-7. The value 0 indicates no contribution from the primary color component.
*/
public Color(int r, int g, int b);
/* Creates a color with the specified red, green, and blue components. The three arguments must each be in the range 0-255.
*/
// Methods
public Color brighter();
public Color darker();
public boolean equals(Object obj);
public int getBlue();
public static Color getColor(String nm);
public static Color getColor(String nm, Color v);
public static Color getColor(String nm, int v);
public int getGreen();
public static Color getHSBColor(float h, float s, float b);
public int getRed();
public int getRGB();
public int hashCode();
public static int HSBtoRGB(float hue, float saturation, float brightness);
public static float[] RGBtoHSB(int r, int g, int b, float hsbvals[]);
public String toString();
}
Table
4.9
The Component class is the abstract superclass of many of the Abstract Window Toolkit classes. With the aid of this class we can position, resize, and can be painted something on the screen, and can receive input events from mouse keyboar etc. This class enriched of number of methods which are listed below :
public abstract class java.awt.Component extends java.lang.Object
implements java.awt.image.ImageObserver
{
// Methods
public boolean action(Event evt, Object what);
public void addNotify();
public Rectangle bounds();
public int checkImage(Image image, ImageObserver observer);
public int checkImage(Image image, int width, int height, ImageObserver observer);
public Image createImage(ImageProducer producer);
public Image createImage(int width, int height);
public void deliverEvent(Event evt);
public void disable();
public void enable();
public void enable(boolean cond);
public Color getBackground();
public ColorModel getColorModel();
public Font getFont();
public FontMetrics getFontMetrics(Font font);
public Color getForeground();
public Graphics getGraphics();
public Container getParent();
public ComponentPeer getPeer();
public Toolkit getToolkit();
public boolean gotFocus(Event evt, Object what);
public boolean handleEvent(Event evt);
public void hide();
public boolean imageUpdate(Image img, int flags, int x, int y,int w, int h);
public boolean inside(int x, int y);
public void invalidate();
public boolean isEnabled();
public boolean isShowing();
public boolean isValid();
public boolean isVisible();
public boolean keyDown(Event evt, int key);
public boolean keyUp(Event evt, int key);
public void layout();
public void list();
public void list(PrintStream out);
public void list(PrintStream out, int indent);
public Component locate(int x, int y);
public Point location();
public boolean lostFocus(Event evt, Object what);
public Dimension minimumSize();
public boolean mouseDown(Event evt, int x, int y);
public boolean mouseDrag(Event evt, int x, int y);
public boolean mouseEnter(Event evt, int x, int y);
public boolean mouseExit(Event evt, int x, int y);
public boolean mouseMove(Event evt, int x, int y);
public boolean mouseUp(Event evt, int x, int y);
public void move(int x, int y);
public void nextFocus();
public void paint(Graphics g);
public void paintAll(Graphics g);
protected String paramString();
public boolean postEvent(Event evt);
public Dimension preferredSize();
public boolean prepareImage(Image image, ImageObserver observer);
public prepareImage(Image image, int width, int height,ImageObserver observer);
public void print(Graphics g);
public void printAll(Graphics g);
public void removeNotify();
public void repaint();
public void repaint(int x, int y, int width, int height);
public void repaint(long tm);
public void repaint(long tm, int x, int y,int width, int height);
public void requestFocus();
public void reshape(int x, int y, int width, int height);
public void resize(Dimension d);
public void resize(int width, int height);
public void setBackground(Color c);
public void setFont(Font f);
public void setForeground(Color c);
public void show();
public void show(boolean cond);
public Dimension size();
public String toString();
public void update(Graphics g);
public void validate();
}
Container is the abstract superclass representing all components that can hold other components. Each container may be associated with a LayoutManager instance that determines the position of each of the container's subcomponents.
public abstract class java.awt.Container extends java.awt.Component {
// Methods
public Component add(Component comp);
public Component add(Component comp, int pos);
public Component add(String name, Component comp);
public void addNotify();
public int countComponents();
public void deliverEvent(Event evt);
public Component getComponent(int n);
public Component[] getComponents();
public LayoutManager getLayout();
public Insets insets();
public void layout();
public void list(PrintStream out, int indent);
public Component locate(int x, int y);
public Dimension minimumSize();
public void paintComponents(Graphics g);
protected String paramString();
public Dimension preferredSize();
public void printComponents(Graphics g);
public void remove(Component comp);
public void removeAll();
public void removeNotify();
public void setLayout(LayoutManager mgr);
public void validate();
}
Table
4.11
This class represents a dialog window, a window that takes input from the user. Dialogs are intended to be temporary windows. They present specific timely information to the user, or they allow the user to specify options for the current operation. The AWT sends the dialog window all mouse, keyboard, and focus events that occur over it. By default, the dialog window is invisible. The application must use the show method to cause the dialog window to appear. The default layout for a dialog is BorderLayout.
public class java.awt.Dialog extends java.awt.Window
{
// Constructors
public Dialog(Frame parent, boolean modal);
/* Creates a dialog window that is initially invisible. If the modal flag is true, the dialog window grabs all input from the user.
*/
public Dialog(Frame parent, String title, boolean modal);
/* Creates a titled dialog window that is initially invisible. If the modal flag is true, then the dialog box grabs all input from the user.
*/
// Methods
public void addNotify();
public String getTitle();
public boolean isModal();
public boolean isResizable();
protected String paramString();
public void setResizable(boolean resizable);
public void setTitle(String title);
}
Table
4.12
|
Method |
Description |
|
addNotify() |
This method calls the createDialog method of this object's toolkit in order to create a DialogPeer for this dialog window. This peer allows the application to change the look of a dialog window without changing its functionality. Most applications do not call this method directly. |
|
getTitle() |
Returns: the title of
this dialog window. |
|
isModal() |
Returns: true if this
dialog window is modal; false otherwise. |
|
isResizable() |
Indicates whether this dialog window is resizable.
By default, a dialog window is resizable.
Returns: true if the user can resize this dialog window; false otherwise. |
|
paramString() |
Returns the parameter string representing
the state of this dialog window. This string is useful for debugging. |
|
setResizable(boolean resizable) |
Sets the resizable flag for this dialog window. |
|
setTitle(String title) |
Sets the title of this dialog window. |
This class encapsulates the width and height of a component in a single object.
public class java.awt.Dimension extends java.lang.Object
{
// Member elements
public int height;
// The height of the component.
public int width;
// The width of the component.
// Constructors
public Dimension();
// Creates a Dimension with a width of zero and a height of zero.
public Dimension(Dimension d);
// Creates a Dimension whose width and height are the same as the argument.
public Dimension(int width, int height);
// Creates a Dimension with the specified width and height.
// Methods
public String toString();
// Returns: a string representation of this dimension.
}
This is a platform-independent class that encapsulates user events from the local Graphical User Interface (GUI) platform.
public class java.awt.Event extends java.lang.Object
{
// Member elements
public Object arg;
// An arbitrary argument of the event. The value of this field depends on the type of event.
public int clickCount;
// For MOUSE_DOWN events, this field indicates the number of consecutive clicks. For other events, it is zero.
public Event evt;
// For MOUSE_DOWN events, this field indicates the number of consecutive clicks. For other events, it is zero.
public int id;
/* The type of the event. Possible values for the id field :
public final static int ACTION_EVENT; //This event indicates that the user wants some action to occur.
public final static int GOT_FOCUS; // A component gained the focus.
public final static int KEY_ACTION; // The user has pressed an "action" key.
public final static int KEY_ACTION_RELEASE; //The user has released an "action" key.
public final static int KEY_PRESS; // The user has pressed a normal key.
public final static int KEY_RELEASE; // The user has released a normal key.
public final static int LIST_DESELECT; //An item in a list has been deselected
public final static int LIST_SELECT; //An item in a list has been selected
public final static int LOAD_FILE; // A file loading event.
public final static int LOST_FOCUS; // A component lost the focus.
public final static int MOUSE_DOWN; //The user has pressed the mouse button.
public final static int MOUSE_DRAG; //The user has moved the mouse with a button pushed.
public final static int MOUSE_ENTER; // The mouse has entered a component.
public final static int MOUSE_EXIT; // The mouse has exited a component.
public final static int MOUSE_MOVE; //The mouse has moved with no button pressed.
public final static int MOUSE_UP; // The user has released the mouse button.
public final static int SAVE_FILE; // A file saving event.
public final static int SCROLL_ABSOLUTE; // The user has moved the bubble in a scroll bar.
public final static int SCROLL_LINE_DOWN; //The user has pushed the "line down" area of a scroll bar.
public final static int SCROLL_LINE_UP; // The user has pushed the "line up" area of a scroll bar.
public final static int SCROLL_PAGE_DOWN;//The user has pushed the "page down" area of a scroll bar.
public final static int SCROLL_PAGE_UP; // The user has pushed the "page up"
public final static int WINDOW_DEICONIFY;//The user has asked the window area of a scroll bar.
public final static int WINDOW_DESTROY; // The user has asked the window manager to de-iconify the window.
public final static int WINDOW_EXPOSE; // A window has become exposed. manager to kill the window.
public final static int WINDOW_ICONIFY; //The user has asked the window manager to iconify the window.
public final static int WINDOW_MOVED; // The window has moved.
/*
public int key;
/* The key that was pressed in a keyboard event. Possible values for the key field when the action is KEY_ACTION or KEY_ACTION_RELEASE: /*
public final static int DOWN;
public final static int END;
public final static int F1;
public final static int F2;
public final static int F3;
public final static int F4;
public final static int F5;
public final static int F6;
public final static int F7;
public final static int F8;
public final static int F9;
public final static int F10;
public final static int F11;
public final static int F12;
public final static int HOME;
public final static int LEFT;
public final static int PGDN;
public final static int PGUP;
public final static int RIGHT;
public final static int UP;
public int modifiers;
/* The state of the modifier keys. Possible masks for the modifiers field
public final static int ALT_MASK
/* This flag indicates that the "alt" key was down when the event occurred. For mouse events, this flag indicates that the middle button was pressed or released. */
public final static int CTRL_MASK;
// This flag indicates that the control key was down when the event occurred.
public final static int META_MASK;
// This flag indicates that the meta key was down when the event occurred. For mouse events, this flag indicates that the right button was pressed or released.
public final static int SHIFT_MASK;
// This flag indicates that the shift key was down when the event occurred.
public Object target;
/* The target component. This indicates the component over which the event occurred or with which the event is associated.
*/
public long when;
// The time stamp of the event.
public int x;
// The x coordinate of the event.
public int y;
// The y coordinate of the event.
// Constructors
public Event(Object target, int id, Object arg);
// Creates an Event with the specified target component, event type, and argument.
public Event(Object target, long when, int id, int x, int y,
int key, int modifiers);
/* Creates an Event with the specified target component, time stamp, event type, x and y coordinates, keyboard key, state of the modifier keys, and an argument set to null.
*/
public Event(Object target, long when, int id, int x, int y,
int key, int modifiers, Object arg);
/* Creates an Event with the specified target component, time stamp, event type, x and y coordinates, keyboard key, state of the modifier keys, and argument.
*/
// Methods
public boolean controlDown();
public boolean metaDown();
protected String paramString();
public boolean shiftDown();
public String toString();
public void translate(int dX, int dY);
}
Table
4.14
|
Method |
Description |
|
controlDown() |
Returns: true if this
event indicates that the control key was down; false otherwise. |
|
metaDown() |
Returns: true if this
event indicates that the meta key was down; false otherwise. |
|
paramString() |
Returns the parameter string representing
this event. This string is useful for debugging. |
|
shiftDown() |
Returns: true if this
event indicates that the shift key was down; false otherwise. |
|
toString() |
Returns: a string
representation of this event. |
|
translate(int dX, int
dY) |
Translates this event so that its x and y
position are increased by dx and dy respectively. |
The class FileDialog displays a dialog window from which the user can select a file.Since it is a modal dialog, when its show method is called, it blocks the rest of the application until the user has chosen a file. The AWT sends the file dialog window all mouse, keyboard, and focus events that occur over it.
public class java.awt.FileDialog extends java.awt.Dialog
{
// Member elements
public final static int LOAD;
// This constant value indicates that the file dialog window is intended to determine a file from which to read.
public final static int SAVE;
// This constant value indicates that the file dialog window is intended to determine a file to which to write.
// Constructors
public FileDialog(Frame parent, String title);
/* Creates a file dialog window with the specified title for loading a file. The files shown are those in the current directory.
*/
public FileDialog(Frame parent, String title, int mode);
/* Creates a file dialog window with the specified title for loading or saving a file. The mode argument must have the value LOAD or to SAVE . The value LOAD indicates that the file dialog is finding a file to read. The value SAVE indicates that the file dialog is finding a place to write a file.
*/
// Methods
public void addNotify();
public String getDirectory();
public String getFile();
public FilenameFilter getFilenameFilter();
public int getMode();
protected String paramString();
public void setDirectory(String dir);
public void setFile(String file);
public void setFilenameFilter(FilenameFilter filter);
}
Table 4.15
|
Method |
Description |
|
addNotify() |
This method calls the createFileDialog method of this object's toolkit in order to create a FileDialogPeer for this file dialog window. The peer allows the application to change the look of a file dialog window without changing its functionality. Most applications do not call this method directly.> |
|
getDirectory() |
Returns: the directory
of this dialog. |
|
getFile() |
Returns: the currently
selected file of this file dialog window, or null if none is selected. |
|
getFilenameFilter() |
Determines this file dialog's filename filter. A filename filter allows the user to specify which files appear in the file dialog window.Returns:
this file dialog's filename filter. |
|
getMode() |
Indicates whether this file dialog box is for
loading from a file or for saving to a file. Returns:
the mode of this file
dialog window; the value is either LOAD or Save |
|
paramString() |
Returns the parameter string representing the state
of this file dialog window. This string is useful for debugging.Returns: the parameter string of this
file dialog window. |
|
setDirectory(String dir) |
Sets the directory of this file dialog window to be
the specified directory. |
|
setFile(String file) |
Sets the selected file for this file
dialog window to be the specified file. This file becomes the default file if
it is set before the file dialog window is first shown. |
|
setFilenameFilter(FilenameFilter filter) |
Sets the filename filter for this file dialog window to the specified filter. |
A Flow layout arranges components in a left-to-right flow, much like lines of text in a paragraph. Flow layouts are typically used to arrange buttons in a panel.
public class java.awt.FlowLayout extends java.lang.Object
implements java.awt.LayoutManager
{
// Member elements
public final static int CENTER;
// This value indicates that each row of components should be centered.
public final static int LEFT;
// This value indicates that each row of components should be left justified.
public final static int RIGHT;
// This value indicates that each row of components should be right justified.
// Constructors
public FlowLayout();
// Creates a new flow layout manager with a centered alignment and a default 5-pixel horizontal and vertical gap.
public FlowLayout(int align);
/* Creates a new flow layout manager with the indicated alignment and a default 5-pixel horizontal and vertical gap. The alignment argument must be one of FlowLayout.LEFT, FlowLayout.RIGHT, or FlowLayout.CENTER.
*/
public FlowLayout(int align, int hgap, int vgap);
/* Creates a new flow layout manager with the indicated alignment and the indicated horizontal and vertical gaps. The alignment argument must be one of FlowLayout.LEFT, FlowLayout.RIGHT, or FlowLayout.CENTER.
*/
// Methods
public void addLayoutComponent(String name, Component comp);
public void layoutContainer(Container target);
public Dimension minimumLayoutSize(Container target);
public Dimension preferredLayoutSize(Container target);
public void removeLayoutComponent(Component comp);
public String toString();
}
Table 4.16
|
Method |
Description |
|
addLayoutComponent(String name, Component comp) |
This method is not used by the flow layout manager. |
|
layoutContainer(Container target) |
Lays out the container argument using
this layout.This method lets each component take its preferred size.Most
applications do not call this method directly. This method is called when a
container calls its layout method. |
|
minimumLayoutSize(Container target) |
Determines the minimum size of the target
container using this flow layout. The
minimum width needed to lay out the container's components is the total
minimum width of each of the components, plus (ncomponents + 1) times the
horizontal gap, plus the left and right inset, where ncomponents is the
number of components in the container.
The minimum height needed to lay out the container's components is the
greatest minimum height of the components, plus twice the vertical gap, plus
the top and bottom insets. Most
applications do not call this method directly. This method is called when a
container calls its layout method. Returns
: the minimum dimensions
needed to lay out the subcomponents of the specified container. |
|
preferredLayoutSize(Container target) |
Determines the preferred size of the
target container using this flow layout.The preferred width to
lay out the container's components is the total preferred width of each of
the components, plus (ncomponents + 1) times the horizontal gap, plus the
left and right inset, where ncomponents is the number of components in the
container. The preferred height to lay out the container's components is the
greatest preferred height of the components, plus twice the vertical gap,
plus the top and bottom insets. Most
applications do not call this method directly. This method is called when a
container calls its preferredSize method. Returns
: the preferred
dimensions to lay out the subcomponents of the specified container. |
|
removeLayoutComponent(Component comp) |
Removes the specified component from this layout. Most applications do not call this method directly. This method is called when a container calls its remove,or removeAll |
|
toString() |
Returns : a string
representation of this layout. |
This class represents a font.
public class java.awt.Font extends java.lang.Object
{
// Member elements
protected String name;
// The logical name of this font.
protected int size;
// The point size of this font.
protected int style;
/* The style of the font. This is the sum of the constants PLAIN, BOLD, or ITALIC. Following style are known :
public final static int BOLD;
public final static int ITALIC;
public final static int PLAIN
*/
// Constructors
public Font(String name, int style, int size);
// Creates a new font with the specified name, style, and point size.
// Methods
public boolean equals(Object obj);
public String getFamily();
public static Font getFont(String nm);
public static Font getFont(String nm, Font font);
public String getName();
public int getSize();
public int getStyle();
public int hashCode();
public boolean isBold();
public boolean isItalic();
public boolean isPlain();
public String toString();
}
Table
4.17
|
Method |
Description |
|
equals(Object obj) |
The result is true if and only if the
argument is not null and is a Font object with the same name, same style, and
same point size as this Font. Returns:
true if the objects are
the same; false otherwise. |
|
getFamily() |
Returns: the
platform-specific family name of this font. |
|
getFont(String nm) |
The first argument is treated as the name of a system property to be obtained as if by the method System.getProperty. The string value of this property is then interpreted as a font as described in the getFont method of two argument. If the specified property is not found, null is returned. Returns: the Font value of the property. |
|
getFont(String nm, Font
font) |
The first argument is treated as the name of a system property to be obtained as if by the method System.getProperty The string value of this property is then interpreted as a font. The property value should be one of the following forms:
|
|
getName() |
Returns: the logical
name of this font. |
|
getSize() |
Returns:
the point size of this font. |
|
getStyle() |
Returns: the style of
this font. |
|
hashCode() |
Returns: a hash code
value for this font.
|
|
isBold() |
Returns: true if this
font is bold; false otherwise. |
|
isItalic() |
Returns: true if this
font is italic; false otherwise. |
|
isPlain() |
Returns: true if this
font is neither bold nor italic; false otherwise. |
|
toString() |
Returns:
a string representation of
this font. |
This class represents a font metrics object, which gives information about the rendering of a particular font on a particular screen. When an application asks the AWT to place a character at the position (x, y), the character is placed so that its reference point (shown as the dot in the picture on the right) is put at that position. The reference point specifies a horizontal line called the baseline of the character. In normal printing, the baselines of the characters should align. In addition, every character in a font has an ascent, a descent, and an advance width. The ascent is the amount by which the character ascends above the baseline. The descent is the amount by which the character descends below the baseline.
The advance width indicates the position at which AWT should place the next character. If the current character is placed with its reference point at the position (x, y), and the character's advance width is w, then the following character is placed with its reference point at the position x+w. The advance width is often the same as the width of character's bounding box, but need not be so. It particular, slanted and italic fonts often have characters whose top-right corner extends slightly beyond the advance width.
An array of characters or a string can also have an ascent, a descent, and an advance width. The ascent of the array is the maximum ascent of any character in the array. The descent is the maximum descent of any character in the array. The advance width is the sum of the advance widths of each of the characters in the array. The default implementations of these methods are inefficient; they are usually overridden with more efficient toolkit-specific implementations.
public abstract class java.awt.FontMetrics extends java.lang.Object
{
// Member elements
protected Font font;
// The actual font.
// Constructors
protected FontMetrics(Font font);
/* Creates a new FontMetrics object for finding out height and width information about the specified font and specific character glyphs in that font.
*/
// Methods
public int bytesWidth(byte data[], int off, int len);
public int charsWidth(char data[], int off, int len);
public int charWidth(char ch);
public int charWidth(int ch);
public int getAscent();
public int getDescent();
public Font getFont();
public int getHeight();
public int getLeading();
public int getMaxAdvance();
public int getMaxAscent();
public int getMaxDescent();
public int[] getWidths();
public int stringWidth(String str);
public String toString();
}
Table 4.18
|
Method |
Description |
|
bytesWidth(byte data[] ,int
off, int len) |
Returns: the advance
width of the subarray of the specified byte array in the font described by
this font metric. |
|
charsWidth(char data[], int
off, int len) |
Returns: the advance width of the subarray of the specified char
array in the font described by this font metric. |
|
charWidth(char ch) |
Returns: the advance
width of the specified char in the font described by this font metric. |
|
charWidth(int ch) |
Returns: the advance
width of the specified character in the font described by this font metric. |
|
getAscent() |
Determines the font ascent of the font described by this font metric. The font ascent is the distance from the base line to the top of most alphanumeric characters. Some characters in the font may extend above this distance Returns: the font ascent of the font. |
|
getDescent() |
Determines the font descent of the font described this font metric. The font descent is the distance from the base line to the bottom of most alphanumeric characters. Some characters in the font may extend below this distance. |
|
getFont() |
Returns: the font
described by this font metric. |
|
getHeight() |
Determines the standard height of a line of text in the font described by this font metric. This standard height is the distance between the baseline of adjacent lines of text. It is computed as the sum getLeading() + getAscent() + getDescent() There is no guarantee that lines of text
spaced at this distance must be disjoint; such lines may overlap if some
characters overshoot either the standard ascent or the standard descent. Returns: the standard height of the
font. |
|
getLeading() |
Determines the standard leading of the font described by this font metric. The standard leading (inter-line spacing) is the logical amount of space to be reserved between the descent of one line of text and the ascent of the next line. The height metric is calculated to include this extra space Returns: the standard leading of the font. |
|
getMaxAdvance() |
Returns:
the maximum advance width of
any character in the font, or -1 if the maximum advance is not known. |
|
getMaxAscent() |
Determines the maximum ascent of the font described by this font metric. No character extends further above the baseline than this height.
Returns: the maximum ascent of any character in
the font. |
|
getMaxDescent() |
Determines the maximum descent of the
font described by this font metric. No character extends further below the
baseline than this height. Returns:
the maximum descent of
any character in the font. |
|
getWidths() |
Returns: any array
giving the advance widths of the first 256 characters in the font described
by this font metric. |
|
stringWidth(String str) |
Returns: the advance
width of the specified string in the font described by this font metric. |
|
toString() |
Returns: a string representation of this font metric. |
A frame is a top-level window with a title and a border. A frame can also have a menu bar. The AWT sends the frame all mouse, keyboard, and focus events that occur over it.
public class java.awt.Frame extends java.awt.Window
implements java.awt.MenuContainer
{
// possible cursor types for the setCursor method
public final static int CROSSHAIR_CURSOR;
public final static int DEFAULT_CURSOR;
public final static int E_RESIZE_CURSOR;
public final static int HAND_CURSOR;
public final static int MOVE_CURSOR;
public final static int N_RESIZE_CURSOR;
public final static int NE_RESIZE_CURSOR;
public final static int NW_RESIZE_CURSOR;
public final static int S_RESIZE_CURSOR;
public final static int SE_RESIZE_CURSOR;
public final static int SW_RESIZE_CURSOR;
public final static int TEXT_CURSOR;
public final static int W_RESIZE_CURSOR;
public final static int WAIT_CURSOR;
// Constructors
public Frame();
// Constructs a new frame; it is initially invisible and has no title.
public Frame(String title);
// Constructs a new frame; it is initially invisible and has the specified title.
// Methods
public void addNotify();
public void dispose();
public int getCursorType();
public Image getIconImage();
public MenuBar getMenuBar();
public String getTitle();
public boolean isResizable();
protected String paramString();
public void remove(MenuComponent m);
public void setCursor(int cursorType);
public void setIconImage(Image image);
public void setMenuBar(MenuBar mb);
public void setResizable(boolean resizable);
public void setTitle(String title);
}
Table
4.19
|
Method |
Description |
|
addNotify() |
This method calls the createFrame method of this object's toolkit in order to create a FramePeer for this frame. This peer allows the application to change the look of a frame without changing its functionality. Most applications do not call this method directly. |
|
dispose() |
Disposes of this frame, its menubar, and any system
resources used by this frame. |
|
getCursorType() |
Returns: the cursor type
of this frame. |
|
getIconImage() |
Returns: the icon image
for this frame, or null if this frame doesn't have an icon image. |
|
getMenuBar() |
Returns: the menu bar
for this frame, or null if this frame doesn't have a menu bar. |
|
getTitle() |
Returns: the title of
this frame, or null if this frame doesn't have a title |
|
isResizable() |
Indicates whether this frame is resizable. By
default, all frames are resizable. Returns:
true if the user can resize
this frame; false otherwise. |
|
paramString() |
Returns the parameter string representing the state
of this frame. This string is useful for debugging. Returns: the parameter
string of this frame. |
|
remove(MenuComponent m) |
Removes the specified menu bar from this frame. |
|
setCursor(int cursorType) |
Sets the cursor image for this frame to be one of
the predefined cursors. |
|
setIconImage(Image image) |
Sets the image to display when this frame is iconized.
The default icon is platform specific. Not all platforms support the concept
of iconizing a window. |
|
setMenuBar(MenuBar mb) |
Sets the menubar of this frame to the specified menubar. |
|
setResizable(boolean resizable) |
Determines whether this frame should be resizable.
By default, a frame is resizable. |
|
setTitle(String title) |
Sets the title of this frame to the specified title. |
The Graphics class is the abstract base class for all graphics contexts which allow an application to draw onto components or onto off-screen images. Unless otherwise stated, all graphics operations performed with a graphics context object only modify bits within the graphic context's clipping region. All drawing or writing is done in the current color using the current paint mode and in the current font..
public abstract class java.awt.Graphics
extends java.lang.Object
{
// Constructors
protected Graphics();
/* This constructor is the default contructor for a graphics context. Since Graphics is an abstract class, applications cannot call this constructor directly. Graphics contexts are obtained from other graphics context or are created by a component.
*/
// Methods
public abstract void clearRect(int x, int y, int width, int height);
public abstract void clipRect(int x, int y, int width, int height);
public abstract void copyArea(int x, int y, int width, int height, int dx, int dy);
public abstract Graphics create();
public Graphics create(int x, int y,int width, int height);
public abstract void dispose();
public void draw3DRect(int x, int y, int width, int height, boolean raised);
public abstract void drawArc(int x, int y, int width, int height,int startAngle, int arcAngle);
public void drawBytes(byte data[], int offset, int length, int x, int y);
public void drawChars(char data[], int offset, int length, int x, int y);
public abstract boolean drawImage(Image img, int x, int y,Color bgcolor,ImageObserver observer);
public abstract boolean drawImage(Image img, int x,int y, ImageObserver observer);
public abstract boolean drawImage(Image img, int x, int y,int width, int height, Color bgcolor, ImageObserver observer);
public abstract boolean drawImage(Image img, int x, int y,int width, int height, ImageObserver observer);
public abstract void drawLine(int x1, int y1, int x2, int y2);
public abstract void drawOval(int x, int y, int width, int height);
public abstract void drawPolygon(int xPoints[], int yPoints[],int nPoints);
public void drawPolygon(Polygon p);
public void drawRect(int x, int y,int width, int height);
public abstract void drawRoundRect(int x, int y, int width,int height, int arcWidth, int arcHeight);
public abstract void drawString(String str, int x, int y);
public void fill3DRect(int x, int y, int width, int height,boolean raised);
public abstract void fillArc(int x, int y, int width, int height,int startAngle, int arcAngle);
public abstract void fillOval(int x, int y, int width, int height);
public abstract void fillPolygon(int xPoints[], int yPoints[],int nPoints);
public void fillPolygon(Polygon p);
public abstract void fillRect(int x, int y, int width, int height);
public abstract void fillRoundRect(int x, int y, int width, int height,int arcWidth, int arcHeight);
public void finalize();
public abstract Rectangle getClipRect();
public abstract Color getColor();
public abstract Font getFont();
public FontMetrics getFontMetrics();
public abstract FontMetrics getFontMetrics(Font f);
public abstract void setColor(Color c);
public abstract void setFont(Font font);
public abstract void setPaintMode();
public abstract void setXORMode(Color c1);
public String toString();
public abstract void translate(int x, int y);
}
Table 4.20
|
Method |
Description |
|
clearRect(...) |
Clears the specified rectangle by filling
it with the background color of the screen.This operation does not
use the current paint mode. |
|
clipRect(...) |
Sets a clipping rectangle for this
graphics context. The resulting clipping area is the intersection of the
current clipping area and the specified rectangle Graphics operations performed with this
graphics context have no effect outside the clipping area. |
|
copyArea( ...) |
Copies an area. The source is the rectangle with origin (x, y) , and size specified by the width and height arguments. The destination is the rectangle with origin and (x +dx, y+dy) the same width and height. The clipping rectangle of this graphics context affects only the destination, not the source. |
|
create() |
Returns: a new graphics
context that is a copy of this graphics context. |
|
create(int x, int
y,int width, int height) |
Creates a new graphics context The new
graphics context is identical to this graphics context, except in two
respects: v The new context is translated by (x, y) . That is to say, the point (0, 0) in the new graphics context is the same as (x, y) in this graphics context. v
The graphics context has an additional
clipping rectangle with origin (0, 0)and size specified by
the width and height arguments, in addition to whatever (translated) clipping
rectangle it inherited from this graphics context. |
|
dispose() |
Disposes of this graphics context. The graphics context cannot be used after
being disposed. |
|
draw3DRect( ...) |
Draws a highlighted 3-D rectangle. |
|
drawArc( ...) |
Draws a single circular or elliptical
arc. The center of the arc is the
center of the rectangle whose origin is (x, y) and whose size is specified by the width
and height arguments. The two axes of
the arc are given by the width and height arguments. The arc is drawn from startAngle to startAngle
+ arcAngle. The start angle and arc angle are in degrees, not radians. A
start angle of 0 indicates the 3-o'clock position. A positive arc angle
indicates a counter-clockwise rotation; a negative arc angle indicates a clockwise
rotation. |
|
drawBytes( ...) |
Draws the text given by the specified
byte array using this graphics context's current font and color. The baseline
of the first character is at position (x, y)in this graphics
context's coordinate system. |
|
drawChars( ...) |
Draws the text given by the specified
character array using this graphics context's current font and color. The
baseline of the first character is at position . |
|
drawImage(Image img, int
x, int y, Color
bgcolor,ImageObserver observer) |
Draws the specified image with its top left corner at (x, y) in this graphics context's coordinate space. Transparent pixels in the image are drawn in the specified background color. If the image has not yet been completely loaded, the image observer's imageUpdate method is notified as more of the image becomes available.Returns: true if all bits of the image are available; false otherwise. |
|
drawImage(Image img, int
x, int y,ImageObserver observer) |
Draws the specified image with its top left corner at (x, y) in this graphics context's coordinate space. Transparent pixels in the image do not affect whatever pixels are already there.If the image has not yet been completely loaded, the image observer's imageUpdate method is notified as more of the image becomes available.Returns: true if all bits of the image are available; false otherwise. |
|
drawImage(Image img, int
x, int y,int width, int
height,..) |
Draws the specified image inside the specified rectangle of this graphics context's coordinate space. The image is scaled if necessary. Transparent pixels in the image are drawn in the specified background color. If the image has not yet been completely loaded, the image observer's imageUpdate method is notified as more of the image becomes available.> |
|
drawLine( ...) |
Draws a line from (x1, y1) to (x2, y2) in this graphics context's coordinate system.The line is drawn below and to the right of the logical coordinates |
|
drawOval( ...) |
Draws a circle or an ellipse such that it fits within the rectangle specified by the x,y, width and height arguments. The center of the oval is the center of the rectangle whose origin is (x, y) is this graphics context's coordinate system and whose size is specified by the width and height arguments. |
|
drawPolygon(int xPoints[], int yPoints[],int nPoints) |
Draws a closed polygon defined by an array of x points and y points.This method draws the polygon defined by npoint line segments, where the first npoint-1 line segments are lines segments from (xPoints[i-1], yPoints[i-1]) to(xPoints[i], yPoints[i]), for 1<=i <= nPoints. The last line segment starts at the final point and ends at the first point |
|
drawPolygon(Polygon p) |
Draws a polygon defined by the specified polygon
argument. |
|
drawRect( ...) |
Draws the outline of the specified rectangle using the current color.The left and right edges of the rectangle are at x and x+width respectively. The top and bottom edges of the rectangle are at y and y+height. respectively. |
|
drawRoundRect( ...) |
Draws an outlined round-cornered rectangle using this graphics context's current color. The left and right edges of the rectangle are at x and x + width respectively. The top and bottom edges of the rectangle are at y and y +height. |
|
drawString( ...) |
Draws the string using this graphics context's current font and color. The baseline of the first character is at position(x, y) in the graphics context's coordinate system. |
|
fill3DRect( ...) |
Draws a highlighted 3-D rectangle that is filled
with this graphics context's current color. |
|
fillArc(...) |
Draws a single circular or elliptical arc that is filled with this graphics context's current color. The result is a pie shape. The center of the arc is the center of the rectangle whose origin is (x, y)and whose size is specified by the width and height arguments. The two axes of the arc are given by the width and height arguments. The arc is drawn from startAngle to startAngle + arcAngle. The start angle and arc angle are in degrees, not radians. A start angle of 0 indicates the 3-o'clock position. A positive arc angle indicates a counter-clockwise rotation; a negative arc angle indicates a clockwise rotation. |
|
fillOval( ...) |
Draws a filled circle or a filled ellipse using this graphics context's current color. The center of the oval is the center of the rectangle whose origin is (x, y) is the graphics context's coordinate system and whose size is specified by the width and height arguments. |
|
fillPolygon(int xPoints[], int yPoints[], int nPoints) |
Fills a polygon defined by an array of x points and y points with this graphics context's current color. This method fills the polygon defined by npoint line segments, where the first npoint-1 line segments are lines segments from (xPoints[i-1], yPoints[i-1]) to (xPoints[i], yPoints[i]), for 1<= I <= nPoints. The last line segment starts at the final point and ends at the first point. The area inside the polygon is defined using an "even-odd" fill rule, also known as the "alternating rule." |
|
fillPolygon(Polygon p) |
Fills a polygon defined by the specified
polygon argument with this graphics context's current color. The area inside
the polygon is defined using an "even-odd" fill rule, also known as
the "alternating rule." |
|
fillRect( ...) |
Fills the specified rectangle with this graphics context's current color. The left and right edges are at x and x +width -1 respectively. The top and bottom edges are at y and y + height -1 respectively. |
|
fillRoundRect( ....) |
Fills an outlined rounded corner rectangle with this graphics context's current color. The left and right edges are at x and x + width - 1 respectively. The top and bottom edges are at y and y + height - 1 respectively. |
|
finalize() |
The finalize method ensures that this graphics context's dispose method is called when this graphics context is no longer referenced. |
|
getClipRect() |
Returns: the bounding
rectangle of this graphics context's clipping area. |
|
getColor() |
Returns: this graphics
context's current color. |
|
getFont() |
Returns: this graphics
context's current font. |
|
getFontMetrics() |
Returns: this font
metrics of the graphics context's current font. |
|
getFontMetrics(Font f) |
Returns: the font
metrics for the specified font. |
|
setColor(Color c) |
Sets this graphics context's current
color to the specified color. All subsequent graphics operations using this
graphics context use this specified color. |
|
setFont(Font font) |
Sets this graphics context's font to the specified font. All subsequent text operations (such as drawString, drawBytes , and drawChars ) using this graphics context use this font. |
|
setPaintMode() |
Sets the paint mode of this graphics context to
overwrite the destination with this graphics context's current color. |
|
setXORMode(Color c1) |
Sets the paint mode of this graphics
context to alternate between this graphics context's current color and the
new specified color. When drawing
operations are performed, pixels which are the current color are changed to
the specified color and vice versa. Pixels
that are of colors other than those two colors are changed in an
unpredictable, but reversible manner; if the same figure is drawn twice then
all pixels are restored to their original values. |
|
toString() |
Returns:
a string representation of this graphics context. |
|
translate(int x, int
y) |
Modifies this graphics context so that
its new origin corresponds to the point (x,y)in this graphics
context's original coordinate system. |
The GridBagConstraints class specifies constraints for components that are laid out using the GridBagLayout class.
public class java.awt.GridBagConstraints extends java.lang.Object implements java.lang.Cloneable { // Member elements public int anchor; /* This field is used when the component is smaller than its display area. It determines where, within the area, to place the component. Valid values are the following : public final static int CENTER; public final static int EAST; public final static int NORTH; public final static int NORTHEAST; public final static int NORTHWEST; public final static int SOUTH; public final static int SOUTHEAST; public final static int SOUTHWEST; public final static int WEST; The default value is GridBagConstraints.CENTER. */ public int fill; /* the fill field has one of the following values : public final static int BOTH; public final static int HORIZONTAL; public final static int NONE; public final static int VERTICAL; This field is used when the component's display area is larger than the component's requested size. It determine whether to resize the component, and if so, how .Valid values are the following :GridBagConstraint.NONE : Do not resize the component. GridBagConstraint.HORIZONTAL : Make the component wide enough to fill its display area horizontally, but don't change its height. GridBagConstraint.VERTICAL : Make the component tall enough to fill its display area vertically, but don't change its width. GridBagConstraint.BOTH : Make the component fill its display area entirely. The default value is GridBagConstraint.NONE. */ public int gridheight; /* Specifies the number of cells in a column for the component's display area. Use GridBagConstraints.REMAINDER to specify that the component be the last one in its column. Use GridBagConstraints.RELATIVE to specify that the component be the next to last one in its column. The default value is 1. */ public int gridwidth; /* Specifies the number of cells in a row for the the component's display area.. Use GridBagConstraints.REMAINDER to specify that the component be the last one in its row. Use GridBagConstraints.RELATIVE to specify that the component be the next to last one in its row. The default value is 1. */ public int gridx; /* Specifies the cell at the left of the component's display area, where the leftmost cell has gridx = 0. The value. GriddBagConstraints.RELATIVE specifies that the component be placed just to the right of the component that was added to the container just before this component was added. The default value is GridBagConstraints.RELATIVE. */ public int gridy; /* Specifies the cell at the top of the component's display area, where the topmost cell has gridy = 0. The value GridBagConstraints.RELATIVE specifies that the component be placed just below the component that was added to the container just before this component was added. The default value is GridBagConstraints.Relative. */ /* Note : Possible values for gridheight, gridwidth, gridx, gridy : public final static int REMAINDER; public final static int RELATIVE; */ public Insets insets; /* This field specifies the external padding of the component, the minimum amount of space between the component and the edges of its display area. The default value is new Insets(0, 0, 0, 0); */ public int ipadx; /* This field specifies the internal padding, that is how much space to add to the minimum size of the component. The width of the component is at least its minimum width plus ipadx*2 pixels. The default value is 0. */ public int ipady; /* This field specifies the internal padding, how much to add to the minimum size of the component. The height of the component is at least its minimum height plus ipadx*2 pixels. The default value is 0. */ public double weightx; /* This field specifies how to distribute extra vertical space. The grid bag layout manager calculates the weight of a row to be the maximum weightx of all the components in a row. If the resulting layout is smaller vertically than the area it needs to fill, the extra space is distributed to each row in proportion to its weight. A row that has weight 0 receives no extra space. If all the weights are zero, all the extra space appears between the grids of the cell and the top and bottom edges. The default value of this field is zero. */ public double weighty; /* This field specified how to distribute extra horizontal space. The grid bag layout manager calculates the weight of a column to be the maximum weighty of all the components in a row. If the resulting layout is smaller horizontally than the area it needs to fill, the extra space is distributed to each column in proportion to its weight. A column that has weight 0 receives no extra space. If all the weights are zero, all the extra space appears between the grids of the cell and the right and left edges. The default value of this field is zero. */ // Constructors public GridBagConstraints(); // Creates a grid bag constraint object with all the fields set to their default value. // Methods public Object clone(); // Returns : a copy of this grid bag constraint. }
The grid bag layout manager is a flexible layout manager that aligns components horizontally and vertically, without requiring that the components be the same size. Each grid bag layout manager uses a rectangular grid of cells, with each component occupying one or more cells (called its display area). Each component in a grid bag layout is associated with a set of constraints contained within a GridBag-Constraints instance that specifies how the component is to be laid out within its display area. The manner in which the grid bag layout manager places a set of components depends on each component's constraints and its minimum size, as well as the preferred size of the components' container. To use a grid bag layout effectively, one or more components must have a customized GridBagConstraints objects created for it.
public class java.awt.GridBagLayout extends java.lang.Object
implements java.awt.LayoutManager
{
// Member elements
protected final static int MAXGRIDSIZE;
/* MAXGRIDSIZE = 128 : The maximum number of grid positions (both horizontally and vertically) that can be laid out by the grid bag layout.
*/
protected final static int MINSIZE;
// MINSIZE = 1 : The smallest grid that can be laid out by the grid bag layout.
// Constructors
public GridBagLayout();
// Creates a grid bag layout manager.
// Methods
public void addLayoutComponent(String name, Component comp);
public GridBagConstraints getConstraints(Component comp);
public void layoutContainer(Container target);
protected GridBagConstraints lookupConstraints(Component comp);
public Dimension minimumLayoutSize(Container target);
public Dimension preferredLayoutSize(Container target);
public void removeLayoutComponent(Component comp);
public void setConstraints(Component comp, GridBagConstraints constraints);
public String toString();
}
Table 4.21
|
Method |
Description |
|
clearRect(...) |
Clears the specified rectangle by filling it with the background color of the screen. This operation does not use the current paint mode. |
|
clipRect(...) |
Sets a clipping rectangle for this
graphics context. The resulting clipping area is the intersection of the
current clipping area and the specified rectangle Graphics operations performed with this
graphics context have no effect outside the clipping area. |
|
copyArea( ...) |
Copies an area. The source is the rectangle with origin (x, y), and size specified by the width and height arguments. The destination is the rectangle with origin and (x +dx, y+dy) the same width and height. The clipping rectangle of this graphics context affects only the destination, not the source. |
|
create() |
Returns: a new graphics
context that is a copy of this graphics context. |
|
create(int x, int
y,int width, int height) |
Creates a new graphics context The new
graphics context is identical to this graphics context, except in two
respects:
|
|
dispose() |
Disposes of this graphics context. The graphics context cannot be used after
being disposed. |
|
draw3DRect( ...) |
Draws a highlighted 3-D rectangle. |
|
drawArc( ...) |
Draws a single circular or elliptical arc. The center of the arc is the center of the rectangle whose origin is (x, y) and whose size is specified by the width and height arguments. The two axes of the arc are given by the width and height arguments. The arc is drawn from startAngle to startAngle + arcAngle. The start angle and arc angle are in degrees, not radians. A start angle of 0 indicates the 3-o'clock position. A positive arc angle indicates a counter-clockwise rotation; a negative arc angle indicates a clockwise rotation. |
|
drawBytes( ...) |
Draws the text given by the specified byte array using this graphics context's current font and color. The baseline of the first character is at position (x, y)in this graphics context's coordinate system. |
|
drawChars( ...) |
Draws the text given by the specified character array using this graphics context's current font and color. The baseline of the first character is at position (x, y) in the graphics context's coordinate system. |
|
drawImage(Image img, int
x, int y, Color
bgcolor,ImageObserver observer) |
Draws the specified image with its top left corner at (x, y) in this graphics context's coordinate space. Transparent pixels in the image are drawn in the specified background color. If the image has not yet been completely loaded, the image observer's imageUpdate method is notified as more of the image becomes available.Returns: true if all bits of the image are available; false otherwise. |
|
drawImage(Image img, int
x, int y,ImageObserver observer) |
Draws the specified image with its top left corner at (x, y) in this graphics context's coordinate space. Transparent pixels in the image do not affect whatever pixels are already there.If the image has not yet been completely loaded, the image observer's imageUpdate method is notified as more of the image becomes available.Returns: true if all bits of the image are available; false otherwise. |
|
drawImage(Image img, int
x, int y,int width, int
height,..) |
Draws the specified image inside the specified rectangle of this graphics context's coordinate space. The image is scaled if necessary. Transparent pixels in the image are drawn in the specified background color. If the image has not yet been completely loaded, the image observer's imageUpdate method is notified as more of the image becomes available. |
|
drawLine( ...) |
Draws a line from (x1, y1) to (x2, y2) in this graphics context's coordinate system.The line is drawn below and to the right of the logical coordinates. |
|
drawOval( ...) |
Draws a circle or an ellipse such that it fits within the rectangle specified by the x,y, width and height arguments. The center of the oval is the center of the rectangle whose origin is (x, y) is this graphics context's coordinate system and whose size is specified by the width and height arguments. |
|
drawPolygon(int xPoints[], int yPoints[],int nPoints) |
Draws a closed polygon defined by an array of x points and y points. This method draws the polygon defined by npoint line segments, where the first npoint-1 line segments are lines segments from (xPoints[i-1], yPoints[i-1]) to (xPoints[i], yPoints[i]), for 1<=i <= nPoints . The last line segment starts at the final point and ends at the first point> |
|
drawPolygon(Polygon p) |
Draws a polygon defined by the specified polygon
argument. |
|
drawRect( ...) |
Draws the outline of the specified rectangle using the current color. The left and right edges of the rectangle are at x and x+width respectively. The top and bottom edges of the rectangle are at y and y+height respectively. |
|
drawRoundRect( ...) |
Draws an outlined round-cornered rectangle using this graphics context's current color. The left and right edges of the rectangle are at x and x + width respectively. The top and bottom edges of the rectangle are at y and y +height. |
|
drawString( ...) |
Draws the string using this graphics context's
current font and color. The baseline of the first character is at position (x, y) in the graphics context's
coordinate system. |
|
fill3DRect( ...) |
Draws a highlighted 3-D rectangle that is filled
with this graphics context's current color. |
|
fillArc(...) |
Draws a single circular or elliptical arc
that is filled with this graphics context's current color. The result is a
pie shape. The center of the arc is
the center of the rectangle whose origin is (x, y)and whose size is
specified by the width and height arguments. The two axes of the arc are
given by the width and height arguments. The arc is drawn from startAngle to startAngle
+ arcAngle. The start angle and arc angle are in degrees, not radians. A start angle of 0 indicates the
3-o'clock position. A positive arc angle indicates a counter-clockwise
rotation; a negative arc angle indicates a clockwise rotation. |
|
fillOval( ...) |
Draws a filled circle or a filled ellipse
using this graphics context's current color. The center of the oval is the center of the
rectangle whose origin is (x, y) is the graphics context's
coordinate system and whose size is specified by the width and height
arguments. |
|
fillPolygon(int xPoints[], int yPoints[], int nPoints) |
Fills a polygon defined by an array of x
points and y points with this graphics context's current color. This method
fills the polygon defined by npoint line segments, where the first npoint-1
line segments are lines segments from (xPoints[i-1], yPoints[i-1]) to (xPoints[i], yPoints[i]),
for 1<= I <= nPoints.The last line segment
starts at the final point and ends at the first point.
The area inside the polygon is defined
using an "even-odd" fill rule, also known as the "alternating
rule." |
|
fillPolygon(Polygon p) |
Fills a polygon defined by the specified
polygon argument with this graphics context's current color. The area inside
the polygon is defined using an "even-odd" fill rule, also known as
the "alternating rule." |
|
fillRect( ...) |
Fills the specified rectangle with this graphics context's current color. The left and right edges are at x and x +width -1 respectively. The top and bottom edges are at y and y + height -1 respectively. |
|
fillRoundRect( ....) |
Fills an outlined rounded corner rectangle with this graphics context's current color. The left and right edges are at x and x + width - 1 respectively. The top and bottom edges are at y and y + height - 1 respectively. |
|
finalize() |
The finalize method ensures that this graphics context's dispose method is called when this graphics context is no longer referenced. |
|
getClipRect() |
Returns: the bounding
rectangle of this graphics context's clipping area. |
|
getColor() |
Returns: this graphics
context's current color. |
|
getFont() |
Returns: this graphics
context's current font. |
|
getFontMetrics() |
Returns: this font
metrics of the graphics context's current font. |
|
getFontMetrics(Font f) |
Returns: the font
metrics for the specified font. |
|
setColor(Color c) |
Sets this graphics context's current
color to the specified color. All subsequent graphics operations using this
graphics context use this specified color. |
|
setFont(Font font) |
Sets this graphics context's font to the specified font. All subsequent text operations (such as drawString, drawBytes , and drawChars ) using this graphics context use this font. |
|
setPaintMode() |
Sets the paint mode of this graphics context to
overwrite the destination with this graphics context's current color. |
|
setXORMode(Color c1) |
Sets the paint mode of this graphics
context to alternate between this graphics context's current color and the
new specified color. When drawing
operations are performed, pixels which are the current color are changed to
the specified color and vice versa. Pixels
that are of colors other than those two colors are changed in an
unpredictable, but reversible manner; if the same figure is drawn twice then
all pixels are restored to their original values. |
|
toString() |
Returns:
a string representation of this graphics context. |
|
translate(int x, int
y) |
Modifies this graphics context so that
its new origin corresponds to the point (x,y) in this graphics
context's original coordinate system. |
This grid layout manager causes the container's components to be laid out in a rectangular grid. The container is split into equal-sized rectangles: one component is placed into each rectangle.
public class java.awt.GridLayout extends java.lang.Object
implements java.awt.LayoutManager
{
// Constructors
public GridLayout(int rows, int cols);
/* Creates a grid layout with the specified number of rows and columns. All components in the layout are given equal size. One, but not both of rows and columns can be zero, which means that any number of objects can be placed in a row or in a column.
*/
public GridLayout(int rows, int cols, int hgap, int vgap);
/* Creates a grid layout with the specified number of rows and columns. All components in the layout are given equal size.In addition the horizontal and vertical gaps are set to the specified values. The horizontal gaps are placed at the left and right edge, and between each of the columns. The vertical gaps are placed at the top and bottom edge, and between each of the rows. One, but not both of rows and columns can be zero, which means that any number of objects can be placed in a row or in a column.
*/
// Methods
public void addLayoutComponent(String name, Component comp);
public void layoutContainer(Container target);
public Dimension minimumLayoutSize(Container target);
public Dimension preferredLayoutSize(Container target);
public void removeLayoutComponent(Component comp);
public String toString();
}
Table 4.22
|
Method |
Description |
|
addLayoutComponent( ...) |
This method is not used by the grid layout manager. |
|
layoutContainer(Container target) |
|
|
minimumLayoutSize(Container target) |
Lays out the container argument using
this layout. This method reshapes the components in the specified target
container in order to satisfy the constraints of the GridLayout object. The grid layout
manager determines the size of individual components by dividing the free
space in the container into equal-sized portions according to the number of
rows and columns in the layout. The container's free space equals the
container's size minus any insets and any specified horizontal or vertical
gap. All components in a grid layout are given the same size. Most
applications do not call this method directly. This method is called when a
container calls its layout method. |
|
preferredLayoutSize(Container target) |
Determines the preferred size of the
container argument using this grid layout. The preferred width of a grid
layout is the largest preferred width of any of the widths in the container
times the number of columns, plus the horizontal padding times the number of
columns plus 1, plus the left and right insets of the target container. The preferred height of a grid layout is
the largest preferred height of any of the widths in the container times the
number of rows, plus the vertical padding times the number of rows plus 1,
plus the top and left insets of the target container. Most applications do not call this method
directly. This method is called when a container calls its preferredSize
method. Returns: the preferred
dimensions to lay out the subcomponents of the specified container. |
|
removeLayoutComponent(Component comp) |
This method is not used by the grid layout manager. |
|
toString() |
Returns: a string
representation of this grid layout. |
The abstract class Image is the superclass of all classes that represent graphical images.
public abstract class java.awt.Image extends java.lang.Object
{
// Member elements
public final static Object UndefinedProperty;
/* The UndefinedProperty object should be returned whenever a property which was not defined for a particular image is fetched.
*/
// Constructors
public Image();
// The default constructor for an image.
// Methods
public abstract void flush();
public abstract Graphics getGraphics();
public abstract int getHeight(ImageObserver observer);
public abstract Object getProperty(String name, ImageObserver observer);
public abstract ImageProducer getSource();
public abstract int getWidth(ImageObserver observer)
}
Table 4.22
|
Method |
Description |
|
flush() |
Flushes all resources being used by this
Image object. These resources includes
any pixel data that is being cached for rendering to the screen as well as
any system resources that are being used to store data or pixels for the
image. The Image object is reset to a
state similar to when it was first created so that if it is again rendered,
the image data must be recreated or fetched again from its source. |
|
getGraphics() |
Creates a graphics context for drawing to an off-screen image. This method can only be called for off-screen images, which are created with the createImage method with two integer arguments. Returns: a graphics context to draw to the off-screen image. |
|
getHeight(ImageObserver observer) |
Determines the height of this image. If
the height is not yet known, the observer is notified later. Returns: the height of the image, or -1 if the height
is not yet known. |
|
getProperty(String name, ImageObserver observer) |
Gets a property of this image by
name. Individual property names are
defined by the various image formats. If a property is not defined for a
particular image, this method returns the UndefinedProperty object. If the properties for this image are not
yet known, this method returns null and the ImageObserver object is notified
later. The property name "comment"
should be used to store an optional comment which can be presented to the
application as a description of the image, its source, or its author. Returns: the value of the named
property. |
|
getSource() |
Returns: the image producer that produces the pixels for this image |
|
getWidth(ImageObserver observer) |
Determines the width of this image. If
the width is not yet known, the observer is notified later. Returns: the width of this image, or
-1 if the width is not yet known. |
The Insets object is a representation of the borders of a container. It specifies the space that a container must leave at each of its edges. The space can either be a border, blank space, or a title.
public class java.awt.Insets extends java.lang.Object
implements java.lang.Cloneable
{
// Member elements
public int bottom; // The inset from the bottom.
public int left; // The inset from the left.
public int right; // The inset from the right.
public int top; // The inset from the top.
// Constructors
public Insets(int top, int left, int bottom, int right);
// Creates and initializes a new Inset with the specified top, left, bottom, and right insets.
// Methods
public Object clone(); // Returns : a copy of this inset.
public String toString(); // Returns : a string representation of this inset.
}
A label is a component for placing text in a container. The text can be changed by the application, but a user cannot edit it directly
public class java.awt.Label extends java.awt.Component
{
// Member elements
public final static int CENTER; // Indicates that the label should be centered.
public final static int LEFT; // Indicates that the label should be left justified.
public final static int RIGHT;// Indicates that the label should be right justified.
// Constructors
public Label(); // Constructs an empty label with whose text is left justified.
public Label(String label); // Constructs a new label with the specified string of text left justified.
public Label(String label, int alignment);
/* Constructs a new label with the specified string of text and the specified alignment. The alignment value must be one of Label.LEFT, Label.RIGHT, or Label.CENTER.
*/
// Methods
public void addNotify();
public int getAlignment();
public String getText();
protected String paramString();
public void setAlignment(int alignment);
public void setText(String label);
}
Table 4.23
|
Method |
Description |
|
addNotify() |
This method calls the createLabel method of this object's toolkit in order to create a LabelPeer for this label. This peer allows the application to change the look of a label without changing its functionality. Most applications do not call this method directly. |
|
getAlignment() |
Returns: the current
alignment of this label. |
|
getText() |
Returns: the text of
this label. |
|
paramString() |
Returns the parameter string representing the state
of this label. This string is useful for debugging. |
|
setAlignment(int alignment) |
Sets the alignment for this label to the specified
alignment. Throws : IllegalArgumentException, if the improper alignment was given. |
|
setText(String label) |
Sets the text for this label to the specified text. |
The List component presents the user with a scrolling list of text items. The list can be set up either so that the user can pick one item or to pick multiple items.
Clicking on an item that isn't selected selects it. Clicking on an item that is already selected deselects it.. Selecting any item causes any other selected item to be automatically deselected. When an item is clicked and becomes selected, AWT sends a list select event to the scrolling list. When an item is clicked and becomes deselected, AWT sends a list deselect event to the scrolling list. The event's target is the scrolling list, and its object is an Integer giving the index of the item in the list. When the user double clicks on an item in a scrolling list, AWT sends an action event to the scrolling list after the list select or deselect event. The event's target is the scrolling list, and its object is the string label of the item selected or deselected. When the user hits return inside a scrolling list, AWT also sends an action event to the scrolling list. The event's target is the scrolling list, and its object is the string label of the last item selected or deselected in the scrolling list.
If an application wants to perform some action based on an item being selected or deselected, it must override the handleEvent method of the scrolling list or of one of its containing windows.
public class java.awt.List extends java.awt.Component
{
// Constructors
public List();
// Creates a new scrolling list. Initially there are no visible lines, and only one item can be selected from the list.
public List(int rows, boolean multipleSelections);
/* Creates a new scrolling list initialized to display the specified number of rows. If the multipleSelections argument is true, then the user can select multiple items at a time from the list. If it is false, only one item at a time can be selected.
*/
// Methods
public void addItem(String item);
public void addItem(String item, int index);
public void addNotify();
public boolean allowsMultipleSelections();
public void clear();
public int countItems();
public void delItem(int position);
public void delItems(int start, int end);
public void deselect(int index);
public String getItem(int index);
public int getRows();
public int getSelectedIndex();
public int[] getSelectedIndexes();
public String getSelectedItem();
public String[] getSelectedItems();
public int getVisibleIndex();
public boolean isSelected(int index);
public void makeVisible(int index);
public Dimension minimumSize();
public Dimension minimumSize(int rows);
protected String paramString();
public Dimension preferredSize();
public Dimension preferredSize(int rows);
public void removeNotify();
public void replaceItem(String newValue, int index);
public void select(int index);
public void setMultipleSelections(boolean v);
}
Table 4.24
|
Method |
Description |
|
addItem(String item) |
Adds the specified string to the end of this
scrolling list. |
|
addItem(String item, int
index) |
Adds the specified string to this
scrolling list at the specified position. The index argument is 0-based. If the index
is -1, or greater than or equal to the number of items already in the list,
then the item is added at the end of this list. |
|
addNotify() |
This method calls the createList method of this object's toolkit in order to create a ListPeer for this scrolling list. This peer allows the application to change the look of a scrolling list without changing its functionality. |
|
allowsMultipleSelections() |
Returns: true if this
scrolling list allows multiple selections; false otherwise. |
|
clear() |
Removes all items from this scrolling list. |
|
countItems() |
Returns: the number of
items in this list. |
|
delItem(int position) |
Deletes the item at the specified position from this
scrolling list. |
|
delItems(int start, int
end) |
Deletes the items in the range (start <= item <= end) [NS1] from this scrolling list. |
|
deselect(int index) |
Deselects the item at the specified index
of this scrolling list. If the item at the specified index is not selected,
or if the index is out of range, then the operation is ignored |
|
getItem(int index) |
Returns: the string of
this scrolling list at the specified index. |
|
getRows() |
Returns: the number of
visible lines in this scrolling list. |
|
getSelectedIndex() |
Returns: the index of
the selected item on this scrolling list, or -1 if either no items are
selected or more than one item is selected. |
|
getSelectedIndexes() |
Returns: an array of the
selected indexes of this scrolling list. |
|
getSelectedItem() |
Returns: the selected
item on this scrolling list, or null if either no items are selected or more
than one item is selected. |
|
getSelectedItems() |
Returns: an array of the
selected items on this scrolling list. |
|
getVisibleIndex() |
Returns: the index of
the item in this scrolling list that was last made visible by the
make-Visible method. |
|
isSelected(int index) |
Determines if a specified item in this
scrolling list is selected. No error occurs if the index argument is less
than 0 or greater than or equal to the number of items in this scrolling
list. Returns: true if the item at
the specified index has been selected; false otherwise. |
|
makeVisible(int index) |
Forces the item at the specified index in
this scrolling list to be visible. No error occurs if the index argument is
less than 0 or greater than or equal to the number of items in this scrolling
list. |
|
minimumSize() |
Determines the minimum size of this scrolling list. If the application has specified the number of visible rows, and that number is greater than 0, the peer's minimumSize method is called with the number of rows in order to determine the minimum size. If this scrolling list does not have a peer, or if the number of visible rows is less than or equal to zero, the superclass's minimumSize method is called to determine the minimum size. Returns: the minimum dimensions needed to display this scrolling list. |
|
minimumSize(int rows) |
Determines the minimum size of a scrolling list with the specified number of rows. This scrolling lists's peer's minimumSize method is called with the number of rows in order to determine the minimum size.If this scrolling list does not have a peer the superclass's minimumSize method is called to determine the minimum size. Returns:
the minimum dimensions
needed to display the specified number of rows in a scrolling list. |
|
paramString() |
Returns the parameter string representing
the state of this scrolling list. This string is useful for debugging. Returns: the parameter string of
this scrolling list. |
|
preferredSize() |
Determines the preferred size of this scrolling list. If the application has specified the number of visible rows, and that number is greater than 0, the peer's preferredSize method is called with the number of rows in order to determine the preferred size. If this scrolling list does not have a peer, or if the number of visible rows is less than or equal to zero, the superclass's preferredSize method is called to determine the preferred size.> Returns:
the preferred dimensions
for displaying this scrolling list. |
|
preferredSize(int rows) |
Determines the preferred size of a scrolling list with the specified number of rows. This scrolling lists's peer's preferredSize method is called with the number of rows in order to determine the preferred size. If this scrolling list does not have a peer the superclass's preferredSize method is called to determine the preferred size. Returns:
the preferred dimensions
for displaying the specified number of rows. |
|
removeNotify() |
Notifies this scrolling list to destroy its peer. |
|
replaceItem(String newValue, int index) |
Replaces the item at the given index in the
scrolling list with the new string. |
|
select(int index) |
Selects the item at the specified index in the
scrolling list. |
|
setMultipleSelections(boolean v) |
Sets whether this scolling list allows multiple
selections. |
The MediaTracker class is a utility class to trace the status of a number of media objects. Media objects could include images as well as audio clips, though currently only images are supported. To use the media tracker, create an instance of the MediaTracker class and then call the addImage method for each image to be tracked. In addition each image can be assigned a unique identifier. The identifier controls both the priority order in which the images are fetched as well as identifying unique subsets of the images that can be waited on independently. Images with a lower ID are loaded in preference to those with a higher ID number.
public class java.awt.MediaTracker extends java.lang.Object
{
// Member elements
public final static int ABORTED;
// ABORTED = 2 : Flag indicating the download of some media was aborted.
public final static int COMPLETE;
// COMPLETE = 8 : Flag indicating the download of media completed successfully.
public final static int ERRORED;
// ERRORED = 4 : Flag indicating the download of some media encountered an error.
public final static int LOADING;
// LOADING = 1 : Flag indicating some media is currently being loaded.
// Constructors
public MediaTracker(Component comp);
// Creates a media tracker to track images for a given component.
// Methods
public void addImage(Image image, int id);
public void addImage(Image image, int id, int w, int h);
public boolean checkAll();
public boolean checkAll(boolean load);
public boolean checkID(int id);
public boolean checkID(int id, boolean load);
public Object[] getErrorsAny();
public Object[] getErrorsID(int id);
public boolean isErrorAny();
public boolean isErrorID(int id);
public int statusAll(boolean load);
public int statusID(int id, boolean load);
public void waitForAll();
public boolean waitForAll(long ms);
public void waitForID(int id);
public boolean waitForID(int id, long ms);
}
Table 4.25
|
Method |
Description |
|
addImage(Image image, int id) |
Adds an image to the list of images being
tracked by this media tracker. The image will eventually be rendered at its
default (unscaled) size. |
|
addImage(Image image, int id, int w, int h) |
Adds an image to the list of images being
tracked by this media tracker. The image will eventually be rendered at its
default (unscaled) size. |
|
checkAll() |
Checks to see if all images being tracked by this media tracker have finished loading. This method does not start loading the images if they are not already loading. If there is an error while loading or scaling an image then that image is considered to have finished loading.Use the isErrorAny method or isErrorID method to check for errors. Returns:
true if all
images have finished loading, were aborted or encountered an error; false
otherwise. |
|
checkAll(boolean load) |
Checks to see if all images being tracked by this media tracker have finished loading. If the load flag is true, then start loading any images that are not yet being loaded. If there is an error while loading or scaling an image then that image is considered to have finished loading. Use the isErrorAny method or isErrorID method to check for errors. Returns : true if all images have finished loading, were aborted or encountered an error; false otherwise. |
|
checkID(int id) |
Checks to see if all images tracked by this media tracker that are tagged with the specified identifier have finished loading. This method does not start loading the images if they are not already loading. If there is an error while loading or scaling an image then that image is considered to have finished loading. Use the isErrorAny method or isErrorID method to check for errors. Returns : true if all images have finished loading, were aborted or encountered an error; false otherwise. |
|
getErrorsAny() |
Returns:
an array of media
objects tracked by this media tracker that have encountered an error, or null
if there are none with errors. |
|
getErrorsID(int id) |
Returns: an array of media objects tracked by this media tracker
with the specified identifer that have encountered an error, or null if there
are none with errors. |
|
isErrorAny() |
Returns : true if any of
the images tracked by this media tracker had an error during loading; false
otherwise. |
|
isErrorID(int id) |
Checks the error status of all of the
images tracked by this media tracker with the specified ID. Returns:
true if any of the
images with the specified identifier had an error during loading; false
otherwise. |
|
statusAll(boolean load) |
Calculates and returns the bitwise inclusive OR of
the status of all the media being tracked by this media tracker. The possible
flags are specified by the following four constants : MediaTracker.LOADING MediaTracker.ABORTED MediatTracker.ERRORED MediaTracker.COMPLETE An image that hasn't started loading has
zero as its status. If the load flag is true, then start loading any images
that are not yet being loaded. Returns
: the bitwise inclusive OR of the status of all of the media being
tracked. |
|
statusID(int id, boolean load) |
Calculates and returns the bitwise inclusive OR of the status of all the media tracked by this media tracker with the specified identifier. The possible flags are as above in the statusAll method. An image that hasn't started loading has zero as its status. If the load flag is true, then start loading any images that are not yet being loaded. Returns : the bitwise inclusive OR of the status of all of the media being tracked. |
|
waitForAll() |
Starts loading all images tracked by this media tracker. This method waits until all the images being tracked have finished loading. If there is an error while loading or scaling an image then that image is considered finished loading. Use the isErrorAny method or isErrorID method to check for errors. Throws : InterruptedException, if another thread has interrupted this thread. |
|
waitForAll(long ms) |
Starts loading all images tracked by this media tracker. This method waits until all the images being tracked have finished loading, or until the length of time specified in milliseconds by the ms argument have passed. If there is an error while loading or scaling an image then that image is considered finished loading. Use the isErrorAny method or isErrorID method to check for errors. Returns
: true if all images
were successfully loaded; false otherwise. Throws
: InterruptedException,
of another thread has interrupted this thread. |
|
waitForID(int id) |
Starts loading all images tracked by this media tracker with the specified identifier. This method waits until all the images with the specified identifier have finished loading. If there is an error while loading or scaling an image then that image is considered finished loading. Use the isErrorAny method or isErrorID method to check for errors. Throws : InterruptedException, if another
thread has interrupted this thread. |
|
waitForID(int id, long ms) |
Starts loading all images tracked by this media tracker with the specified identifier. This method waits until all the images with the specified identifier have finished loading, or until the length of time specified in milliseconds by the ms argument have passed . If there is an error while loading or scaling an image then that image is considered finished loading. Use the isErrorAny method or isErrorID method to check for errors. Returns
: true if all images
were successfully loaded; false otherwise. Throws
: InterruptedException,
if another thread has interrupted this thread. |
A menu is a pull-down component of a menu bar. A menu can optionally be a tear-off menu. A tear-off menu can remain on the screen after the mouse button has been released. The mechanism for tearing off a menu is platform dependent. Each item in a menu must belong to the MenuItem class . This can be an instance of MenuItem, a submenu (an instance of Menu), or a check box (an instance of CheckboxMenuItem).
public class java.awt.Menu extends java.awt.MenuItem implements java.awt.MenuContainer { // Constructors public Menu(String label); public Menu(String label, boolean tearOff); // Methods public MenuItem add(MenuItem mi); public void add(String label); public void addNotify(); public void addSeparator(); public int countItems(); public MenuItem getItem(int index); public boolean isTearOff(); public void remove(int index); public void remove(MenuComponent item); public void removeNotify(); }
Table
4.26
|
Method |
Description |
|
add(MenuItem mi) |
Adds the specified menu item to this
menu. If the menu item had been part
of another menu, remove it from that menu. Returns : the menu item added. |
|
add(String label) |
Adds an item with the specified label to
this menu. This method creates a menu item to hold the string. |
|
addNotify() |
This method calls the createMenu method of this object's toolkit in order to create a MenuPeer for this menu. This peer allows the application to change the look of a menu without changing its functionality. Most applications do not call this method directly. |
|
addSeparator() |
Adds a separator line to this menu at the current
position. |
|
countItems() |
Returns : the number of
elements in this menu. |
|
getItem(int index) |
Returns
:the item located at the specified index of this menu. |
|
isTearOff() |
Returns
: true if this is a tear-off menu; false otherwise. |
|
remove(int index) |
Deletes the item at the specified index from this
menu. |
|
remove(MenuComponent item) |
Deletes the specified menu item from this
menu. If the item is not part of the menu, nothing happens. |
|
removeNotify() |
Notifies the menu to destroy its
peer. This menu also notifies each of
its menu items to destroy their peers. |
This class that encapsulates the platform's concept of a menu bar bound to a Frame. In order to attach the menu bar to a frame, the setMenuBar method in class Frame must be called.
public class java.awt.MenuBar extends java.awt.MenuComponent
implements java.awt.MenuContainer
{
// Constructors
public MenuBar();
// Methods
public Menu add(Menu m);
public void addNotify();
public int countMenus();
public Menu getHelpMenu();
public Menu getMenu(int i);
public void remove(int index);
public void remove(MenuComponent m);
public void removeNotify();
public void setHelpMenu(Menu m);
}
Table
4.27
|
Method |
Description |
|
add(Menu m) |
Adds the specified menu to this menu bar. |
|
addNotify() |
This method calls the createMenuBar method of this object's toolkit in order to create a MenuBarPeer for this menu bar. This peer allows the application to change the look of a menu barwithout changing its functionality. Most applications do not call this method directly. |
|
countMenus() |
Returns : the number of menus on this menu bar. |
|
getHelpMenu() |
Returns : the help menu
on this menu bar. |
|
getMenu(int i) |
Returns : the menu at the
specified index of this menu bar |
|
remove(int index) |
Removes the menu located at the specified index from
this menu bar. |
|
remove(MenuComponent m) |
Removes the specified menu component from this menu
bar. |
|
removeNotify() |
Notifies this menu bar to destroy its
peer. This menu bar also notifies each
of its menus to destroy their peers. |
|
setHelpMenu(Menu m) |
Sets the
help menu on this menu bar to be the specified menu. |
The abstract class MenuComponent is the superclass of all menu related components.
public abstract class java.awt.MenuComponent extends java.lang.Object
{
// Constructors
public MenuComponent(); // The default constructor.
// Methods
public Font getFont();
public MenuContainer getParent();
public MenuComponentPeer getPeer();
protected String paramString();
public boolean postEvent(Event evt);
public void removeNotify();
public void setFont(Font f);
public String toString();
}
Table
4.28
|
Method |
Description |
|
getFont() |
Returns : the font used
in this menu component, if there is one; null otherwise. |
|
getParent() |
Returns : the menu component containing this menu
component; null if this is the outermost component, the menu bar itself. |
|
getPeer() |
Returns this menu component's peer. Every
menu component has a peer associated with it. This peer allows the
application to change the look of a menu component without changing its
functionality. Returns : the menu component's peer. |
|
paramString() |
Returns the parameter string representing
the state of this menu component. This string is useful for debugging. Returns : the parameter string of
this menu component. |
|
postEvent(Event evt) |
Posts an event to this menu component, by
calling its handleEvent method. If handleEvent returns false, then post the
event to the menu component's parent. Returns :true, if this menu component or one of its parents
handled the event; false otherwise. |
|
removeNotify() |
Notifies this menu component to destroy its peer. |
|
setFont(Font f) |
Sets the font to be used for this menu
component to the specified font. This font is also used by all subcomponents
of the menu component, unless those subcomponents specify a different font. |
|
toString() |
Returns : a string
representation of this menu component. |
All items in a menu must belong to MenuItem class or a subclass. The default menu item represents a simple labeled menu item. When a menu item is selected, the AWT sends an action event to the menu item's containing frame. The event's target is the menu item, and its object is the string label of the menu item. Note that the subclass Menu overrides this behavior and does not sent any event to the frame until one of its subitems is selected.
public class java.awt.MenuItem extends java.awt.MenuComponent
{
// Constructors
public MenuItem(String label);
/* Constructs a new menu item with the specified label. The label "-" is reserved to mean a separator between menu items. By default, all menu items except for separators are enabled.
*/
// Methods
public void addNotify();
public void disable();
public void enable();
public void enable(boolean cond);
public String getLabel();
public boolean isEnabled();
public String paramString();
public void setLabel(String label);
}
Table
4.29.
|
Method |
Description |
|
addNotify() |
This method calls the createMenuItem method of this object's toolkit in order to create a MenuItemPeer for this menu item. This peer allows the application to change the look of a menu item,without changing its functionality. Most applications do not call this method directly. |
|
disable() |
Disables this menu item. It can no longer
be selected by the user. |
|
enable() |
Enables this menu item; it can be
selected by the user. |
|
enable(boolean cond) |
Enables this menu item if the flag is
true; otherwise, disables it. |
|
getLabel() |
Returns : the label of
this menu item, or null if this menu item has no label. |
|
isEnabled() |
Checks whether this menu item is enabled.
Returns : true if this menu item
is enabled; false otherwise |
|
paramString() |
Returns the parameter string representing
the state of this menu item. This string is useful for debugging. |
|
setLabel(String label) |
Changes this menu item's label to be the label argument. |
A Panel is the simplest container class. It provides space into which an application can attach any other component, including other panels. The AWT sends the panel all mouse, keyboard, and focus events that occur over it. The default layout manager for a Panel is the FlowLayout layout manager.
public class java.awt.Panel extends java.awt.Container
{
// Constructors
public Panel(); // Creates a new panel. The default layout for a panel is FlowLayout.
// Methods
public void addNotify();
/* This method calls the createPanel method of this object's toolkit in order to create a PanelPeer for this panel. This peer allows the application to change the look of a panel without changing its functionality.
*/
}
A point represents an (x, y) coordinate.
public class java.awt.Point extends java.lang.Object
{
// Member elements
public int x;
public int y;
// Constructors
public Point(int x, int y); // Constructs and initializes a point to the specified (x, y) coordinate.
// Methods
public boolean equals(Object obj);
public int hashCode();
public void move(int x, int y);
public String toString();
public void translate(int dx, int dy);
}
Table
4.30
|
Method |
Description |
|
equals(Object obj) |
The result is true if and only if the argument is
not null and is a Point object that has the same x and y coordinates as this
object. Returns : true if the objects are the same; false
otherwise. |
|
hashCode() |
Returns : a hash code
value for this point. |
|
move(int x, int
y) |
Modifies this point so that it now represents the
(x, y ) coordinates indicated. |
|
toString() |
Returns : a string representation of this point. |
|
translate(int dx, int
dy) |
Translates this point by dx to the right
and dy downward so that it now represents the point (x +dx, y + dy) , where
it had been representing the point (x, y). |
A polygon consists of a list of (x, y ), where each successive pair of coordinates defines a side of the polygon.
public class java.awt.Polygon extends java.lang.Object
{
// Member elements
public int npoints; // The total number of points.
public int xpoints[]; // The array of x coordinates.
public int ypoints[]; // The array of y coordinates.
// Constructors
public Polygon(); // Creates an empty polygon.
public Polygon(int xpoints[], int ypoints[], int npoints);
// Constructs and initializes a polygon from the specified parameters.
// Methods
public void addPoint(int x, int y);
/* Appends a point to this polygon. If an operation that calculates the bounding box of this polygon (getBoundingBox or inside) has already been performed, this method updates the bounding box.
*/
public Rectangle getBoundingBox(); // Returns : the smallest rectangle that contains this polygon.
public boolean inside(int x, int y);
/* Determines if the specified point is inside this polygon. This method uses an even-odd insideness rule (also known as an "alternating rule") to determine whether the pont (x, y) inside this polygon.
Returns : true if the point ( x, y) is inside this polygon; false otherwise.
*/
}
A rectangle specifies an area defined by its top-left (x, y) coordinate, its width and its height.
public class java.awt.Rectangle extends java.lang.Object
{
// Member elements
public int height; // The height of the rectangle.
public int width; // The width of the rectangle.
public int x; // The x coordinate of the top left corner of the rectangle.
public int y; // The y coordinate of the top left corner of the rectangle.
// Constructors
public Rectangle();
//Constructs a new rectangle whose top-left corner is (0, 0), and whose width and height are 0.
public Rectangle(Dimension d);
/* Constructs a new rectangle whose top-left corner is (0, 0) and whose width and height are specified by the dimension argument.
*/
public Rectangle(int width, int height);
// Constructs a new rectangle whose top-left corner is (0, 0), and whose width and height are the specified arguments
public Rectangle(int x, int y, int width, int height);
// Constructs a new rectangle whose top-left corner is (x, y), and whose width and height are the specified arguments.
public Rectangle(Point p);
// Constructs a new rectangle whose top-left corner is the specified point argument and whose width and height are 0.
public Rectangle(Point p, Dimension d);
/* Constructs a new rectangle whose top-left corner is the specified point argument and and whose width and height are specified by the dimension argument.
*/
// Methods
public void add(int newx, int newy);
public void add(Point pt);
public void add(Rectangle r);
public boolean equals(Object obj);
public void grow(int h, int v);
public int hashCode();
public boolean inside(int x, int y);
public Rectangle intersection(Rectangle r);
public boolean intersects(Rectangle r);
public boolean isEmpty();
public void move(int x, int y);
public void reshape(int x, int y, int width, int height);
public void resize(int width, int height);
public String toString();
public void translate(int dx, int dy);
public Rectangle union(Rectangle r);
}
Table
4.31
|
Method |
Description |
|
add(int newx, int
newy) |
Adds the point (newx, newy) to this rectangle. This rectangle is modified to be the smallest rectangle that contains both this rectangle and the point. |
|
add(Point pt) |
Adds the point to this rectangle. This rectangle is modified to be the
smallest rectangle that contains both this rectangle and the point. |
|
add(Rectangle r) |
Adds the rectangle argument to this
rectangle. This rectangle is modified
to be the smallest rectangle that contains both rectangles. |
|
equals(Object obj) |
The result is true if and only if the
argument is not null and is a Rectangle object that has the same top-left
corner, width, and height as this object.
Returns: true if the objects are the same; false otherwise. |
|
grow(int h, int
v) |
Modifies the rectangle so that it is h units larger on both the left and right size, and v units larger at both the top and bottom The new rectangle has (x-h, y-v) as its top-left corner, a width of (x +2h)and a height of (y + 2v):p> |
|
hashCode() |
Returns: a hash code
value for this object. |
|
inside(int x, int
y) |
Checks if the specified point lies inside this rectangle. Returns: true if the point (x, y) is inside this rectangle; false otherwise. |
|
intersection(Rectangle r) |
Returns: the largest
rectangle contained in both the rectangle argument and in this rectangle. |
|
intersects(Rectangle r) |
Determines if this rectangle and the
rectangle argument intersect. Two rectangles insersect if their intersection
is non-empty. Returns: true if the
rectangle argument and this rectangle insersect; false otherwise. |
|
isEmpty() |
Determines if this rectangle is empty. A
rectangle is empty if its width or its height is less than or equal to zero. Returns: true if this rectangle is empty; false
otherwise. |
|
move(int x, int
y) |
Moves this rectangle so that its new top-left corner is the specified (x, y)coordinate. |
|
reshape( ... ) |
Reshapes this rectangle so that its new top-left corner is the specified (x, y) coordinate and its new width and height are the specified arguments. |
|
resize( .... ) |
Resizes this rectangle so that its new width and
height are the indicated arguments. |
|
toString() |
Returns: a string
representation of this rectangle. |
|
translate(int dx, int
dy) |
Translates this rectangle by dx to the right and dy downward so that its top- left corner is now point (x + dx, y + dy),where it had been the point (x, y). |
|
union(Rectangle r) |
Computes the union of this rectangle with
the argument rectangle. Returns: the smallest rectangle containing both the
rectangle argument and this rectangle. |
A scroll bar provides a convenient means of allowing a user to select from a range of values. Alternatively, a scroll bar can represent a range of values.
public class java.awt.Scrollbar extends java.awt.Component
{
// Member elements
public final static int HORIZONTAL; // Constant indicating to construct a horizontal scroll bar.
public final static int VERTICAL; // Constant indicating to construct a vertical scroll bar.
// Constructors
public Scrollbar(); // Constructs a new vertical scroll bar.
public Scrollbar(int orientation);
/* Constructs a new scroll bar with the specified orientation.The orientation argument must be one of the two values Scrollbar.HORIZONTAL Scrollbar.VERTICAL indicating a horizontal or vertical scroll bar, respectively. Throws : IllegalArgumentException , when an illegal orientation is given.
*/
public Scrollbar(int orientation, int value, int visible,int minimum, int maximum);
/* Constructs a new scroll bar with the specified orientation, initial value, page size, and minumum and maximum values. The orientation argument must be one of the two values Scrollbar.HORIZONTAL Scrollbar.VERTICAL indicating a horizontal or vertical scroll bar, respectively. If the specified maximum value is less than the minimum value, it is changed to be the same as the minimum value. If the initial value is lower than the minimum value, it is changed to be the minimum value; if it is greater than the maximum value, it is changed to be the maximum value.
*/
// Methods
public void addNotify();
public int getLineIncrement();
public int getMaximum();
public int getMinimum();
public int getOrientation();
public int getPageIncrement();
public int getValue();
public int getVisible();
protected String paramString();
public void setLineIncrement(int l);
public void setPageIncrement(int l);
public void setValue(int value);
public void setValues(int value, int visible, int minimum, int maximum);
}
Table 4.32
|
Method |
Description |
|
addNotify |
This method calls the createScrollbar method of this object's toolkit in order to create a ScrollbarPeer for this button. This peer allows the application to change the look of a scroll bar without changing its functionality. Most applications do not call this method directly. |
|
getLineIncrement() |
Determines the line increment of this scrollbar,
which is the amount that is added or subtracted from this scroll bar's value
when the user hits the down or up gadget.
Returns: the line increment of this scroll bar. |
|
getMaximum() |
Returns: the maximum
value of this scroll bar. |
|
getMinimum() |
Returns: the maximum value of this scroll bar. |
|
getOrientation() |
Determines the orientation of this scroll bar. The value returned is either HORIZONTAL or VERTICAL. Returns: the orientation of this scroll bar. |
|
getPageIncrement() |
Determines
the page increment of this scroll bar, which is the amount that is added to
or subtracted from this scroll bar' value when the user hits the page down or
page up gadget. Returns: the page increment for this
scroll bar. |
|
getValue() |
Returns: the current
value of this scroll bar. |
|
getVisible() |
Determines the "visible" amount
of this scroll bar, which is the range of values represented by the width of
the bubble in this scroll bar.
Returns: the "visible"
amount of this scroll bar. |
|
paramString() |
Returns the parameter string representing
the state of this scroll bar. This string is useful for debugging. Returns:
the parameter string of this scroll bar. |
|
setLineIncrement(int l) |
Sets the line increment of this scroll
bar. The line increment is the
value that is added to or subtracted from the value of this scroll bar when
the user hits the line down or line up gadget. |
|
setPageIncrement(int l) |
Sets the page increment of this scroll
bar. The page increment is the value
that is added to or subtracted from the value of the scroll bar when the user
hits the page down or page up gadget. |
|
setValue(int value) |
Sets the value of this scroll bar to the
specified value. If the specified value is below this scroll bar's current
minimum or above the current maximum, it becomes the minimum or maximum
value, respectively. |
|
setValues(int value,..) |
Sets several parameters of this scroll
bar simultaneously. |
A text area is a multiline area for displaying text. It can be set to allow editing or to be read-only.
public class java.awt.TextArea extends java.awt.TextComponent
{
// Constructors
public TextArea(); // Constructs a new text area.
public TextArea(int rows, int cols);
// Constructs a new text area with the specified number of rows and columns.
public TextArea(String text); // Constructs a new text area with the specified text displayed.
public TextArea(String text, int rows, int cols);
// Constructs a new TextArea with the specified text, and the specified number of rows and columns.
// Methods
public void addNotify();
public void appendText(String str);
public int getColumns();
public int getRows();
public void insertText(String str, int pos);
public Dimension minimumSize();
public Dimension minimumSize(int rows, int cols);
protected String paramString();
public Dimension preferredSize();
public Dimension preferredSize(int rows, int cols);
public void replaceText(String str, int start, int end);
}
Table 4.33
|
Method
|
Description |
|
addNotify() |
This method calls the createTextArea method of this object's toolkit in order to create a TextAreaPeer for this text area. This peer allows the application to change the look of a text area without changing its functionality. Most applications do not call this method directly.p> |
|
appendText(String str) |
Appends the given text to this text area's current
text. |
|
getColumns() |
Returns: the number of
columns in this text area. |
|
getRows() |
Returns: the number of
rows in this text area. |
|
insertText(String str, int
pos) |
Inserts the specified text at the specified position
in this text area. |
|
minimumSize() |
Determines the minimum size of this text area. If the application has specified both the number of rows and the number of columns for this text area, and both are greater than zero, then the text area's peer's minimumSize method is called with the number of rows and columns in order to determine the minimum size. If the text area does not have a peer, or if the number of rows or number of columns specified by the application is less than or equal to zero, the superclass's minimumSize method is called to determine the minimum size. Returns: the minimum dimensions needed for this text area. |
|
minimumSize(int rows, int cols) |
Determines the minimum size of a text area with the specified number of rows and columns. This text area's peer's minimumSize method is called with the number of rows and columns in order to determine the minimum size. If this text area does not have a peer, the superclass's minimumSize method is called to determine the minimum size. Returns: the minimum dimensions needed to display the text area with the specified number of rows and columns. |
|
paramString() |
Returns the parameter string representing
the state of this text area. This string is useful for debugging. Returns: the parameter string of this text area. |
|
preferredSize() |
Determines the preferred size of this text area. If the application has specified both the number of rows and the number of columns for this text area, and both are greater than zero, then the text area's peer's preferredSize method is called with the number of rows and columns in order to determine the preferred size. If this text area does not have a peer, or if the number of rows or number of columns specified by the application is less than or equal to zero, the superclass's preferredSize method is called to determine the preferred size. Returns: the preferred dimensions needed for this text area. |
|
preferredSize(int rows, int cols) |
Determines the preferred size of a text area with the specified number of rows and columns. This text area's peer's preferredSize method is called with the number of rows and columns in order to determine the preferred size. If this text area does not have a peer the superclass's preferredSize method is called to determine the preferred size. Returns: the preferred dimensions needed to display the text area with the specified number of rows and columns. |
|
replaceText(String str, int start, int end) |
Replaces the text in the text area from
the start (inclusive) index to the end (exclusive) index with the new text
specified. |
A text component is the superclass of any component that allows the editing of some text.
public class java.awt.TextComponent extends java.awt.Component
{
// Methods
public String getSelectedText();
public int getSelectionEnd();
public int getSelectionStart();
public String getText();
public boolean isEditable();
protected String paramString();
public void removeNotify();
public void select(int selStart, int selEnd);
public void selectAll();
public void setEditable(boolean t);
public void setText(String t);
}
Table 4.34
|
Method
|
Description |
|
getSelectedText() |
Returns: the selected
text in this text component. |
|
getSelectionEnd() |
Returns: selected text's
end position in this text component. |
|
getSelectionStart() |
Returns: the selected text's start position in this
text component. |
|
getText() |
Returns: the text of
this text component. |
|
isEditable() |
Returns: true if this text component is editable;
false otherwise. |
|
paramString() |
Returns the parameter string representing the state
of this text component. This string is useful for debugging. Returns:
the parameter string of this text component. |
|
removeNotify() |
Notifies this text component to destroy its peer. |
|
select(int selStart, int
selEnd) |
Selects the text in this text component found from
the specified start (inclusive) index to the specified end index (exclusive). |
|
selectAll() |
Selects all the text in this text component. |
|
setEditable(boolean t) |
If the boolean argument is true, this text component
becomes user editable. If the flag is false, the user cannot change the text
of this text component. |
|
setText(String t) |
Sets the text of this text component to be the
specified text. |
A text field is a component that presents the user with a single editable line of text.
public class java.awt.TextField extends java.awt.TextComponent
{
// Constructors
public TextField(); // Constructs a new text field.
public TextField(int cols); // Constructs a new text field the specified number of characters wide.
public TextField(String text); // Constructs a new text field initialized with the specified text.
public TextField(String text, int cols);
/* Constructs a new text field initialized with the specified text and wide enough to hold the specified number of characters.
*/
// Methods
public void addNotify();
public boolean echoCharIsSet();
public int getColumns();
public char getEchoChar();
public Dimension minimumSize();
public Dimension minimumSize(int cols);
protected String paramString();
public Dimension preferredSize();
public Dimension preferredSize(int cols);
public void setEchoCharacter(char c);
}
Table 4.35
|
Method |
Description |
|
addNotify() |
This method calls the createTextField method of this object's toolkit in order to create a TextFieldPeer for this text field. This peer allows the application to change the look of a text field without changing its functionality. Most applications do not call this method directly. |
|
echoCharIsSet() |
Returns : true if this
text field has a character set for echoing; false otherwise. |
|
getColumns() |
Returns : the number of columns in this text field. |
|
getEchoChar() |
Returns : the echo
character for this text field. |
|
minimumSize() |
Determines the minimum size of this text field. If the application has specified the number of columns for this text field, and it is greater than zero, then this text field's peer's minimumSize method is called with the number columns in order to determine the minimum size. If this text field does not have a peer, or if the number of columns specified by the application is less than or equal to zero, the superclass's minimumSize method is called to determine the minimum size |
|
minimumSize(int cols) |
Determines the minimum size of a text field with the specified number of columns. This text field's peer's minimumSize method is called with the number of columns in order to determine the minimum size. If this text field does not have a peer the superclass's minimumSize method is called to determine the minimum size. |
|
paramString() |
Returns the parameter string representing
the state of this text field. This string is useful for debugging. |
|
preferredSize() |
Determines the preferred size of this text field. If the application has specified the number of columns for this text field, and it is greater than zero, then this text field's peer's preferredSize method is called with the number of columns in order to determine the preferred size |
|
preferredSize(int cols) |
Determines the preferred size of a text field with the specified number of columns. This text field's peer's preferredSize method is called with the number columns in order to determine the preferred size. |
|
setEchoCharacter(char c) |
Sets the echo character for this text
field. Any character that the user types in the text field is echoed in this
text field as the echo character. An echo character is useful for fields
where the user input shouldn't be echoed to the screen such as in the case of
a text field for typing in a password. |
This class is the abstract superclass of all actual implementations of the Abstract Window Toolkit. Subclasses of the class are used to bind the various components to particular native toolkit implementations. Most applications should not call any of the methods is this class directly. These methods are called by the addNotify methods of the various components in the Abstract Window Toolkit.
public abstract class java.awt.Toolkit extends java.lang.Object
{
// Constructors
public Toolkit();
// The default constructor for a toolkit.
// Methods
public abstract int checkImage(Image image, int width, int height, ImageObserver observer);
protected abstract ButtonPeer createButton(Button target);
protected abstract CanvasPeer createCanvas(Canvas target);
protected abstract CheckboxPeer createCheckbox(Checkbox target);
protected abstract CheckboxMenuItemPeer createCheckboxMenuItem (CheckboxMenuItem target);
protected abstract ChoicePeer createChoice(Choice target);
protected abstract DialogPeer createDialog(Dialog target);
protected abstract FileDialogPeer createFileDialog(FileDialog target);
protected abstract FramePeer createFrame(Frame target);
public abstract Image createImage(ImageProducer producer);
protected abstract LabelPeer createLabel(Label target);
protected abstract ListPeer createList(List target);
protected abstract MenuPeer createMenu(Menu target);
protected abstract MenuBarPeer createMenuBar(MenuBar target);
protected abstract MenuItemPeer createMenuItem(MenuItem target);
protected abstract PanelPeer createPanel(Panel target);
protected abstract ScrollbarPeer createScrollbar(Scrollbar target);
protected abstract TextAreaPeer createTextArea(TextArea target);
protected abstract TextFieldPeer createTextField(TextField target);
protected abstract WindowPeer createWindow(Window target);
public abstract ColorModel getColorModel();
public static Toolkit getDefaultToolkit();
public abstract String[] getFontList();
public abstract FontMetrics getFontMetrics(Font font);
public abstract Image getImage(String filename);
public abstract Image getImage(URL url);
public abstract int getScreenResolution();
public abstract Dimension getScreenSize();
public abstract boolean prepareImage(Image image, int width, int height, ImageObserver observer);
public abstract void sync();
}
Table 4.36
|
Method |
Description |
|
checkImage( ... ) |
If the width and height arguments are both -1, this method returns the status of the construction of a screen representaion of the specified image in this toolkit. Otherwise, this method returns the status of the construction of a scaled representation of the specified image at the specified width and height. This method does not cause the image to begin loading. An application must use the prepareImage method to force the loading of an image. This toolkit method is used by the checkImage methods of Component. Information on the flags returned by this method can be found in. Returns: the bitwise inclusive OR of the ImageObserver flags indicating what information about the image is available. |
|
createButton(Button target) |
Returns: this toolkit's
implementation of a Button. |
|
createCanvas(Canvas target) |
Returns: this toolkit's
implementation of a Canvas. |
|
createCheckbox(Checkbox target) |
Returns: this toolkit's
implementation of a Checkbox. |
|
createCheckboxMenuItem( ... ) |
Returns: this toolkit's
implementation of a CheckboxMenuItem. |
|
createChoice(Choice target) |
Returns: this toolkit's
implementation of a Choice. |
|
createDialog(Dialog target) |
Returns: this toolkit's
implementation of a Dialog. |
|
createFileDialog(FileDialog target) |
Returns: this toolkit's implementation of a FileDialog
. |
|
createFrame(Frame target) |
Returns: this toolkit's
implementation of a Frame |
|
createImage(ImageProducer producer) |
Returns: this toolkit's
implementation of an Image. |
|
createLabel(Label target) |
Returns: this toolkit's
implementation of a Label. |
|
createList(List target) |
Returns: this toolkit's
implementation of a List. |
|
createMenu(Menu target) |
Returns: this toolkit's implementation of a Menu. |
|
createMenuBar(MenuBar target) |
Returns: this toolkit's implementation of a MenuBar |
|
createMenuItem(MenuItem target) |
Returns: this toolkit's implementation of a MenuItem
. |
|
createPanel(Panel target) |
Returns: this toolkit's implementation of a Panel. |
|
createScrollbar(Scrollbar target) |
Returns: this toolkit's
implementation of a ScrollBar . |
|
createTextArea(TextArea target) |
Returns: this toolkit's
implementation of a TextArea. |
|
createTextField(TextField target) |
Returns: this toolkit's
implementation of a TextField. |
|
createWindow(Window target) |
Returns: this toolkit's
implementation of a Window. |
|
getColorModel() |
Determine's the color model of this toolkit's screen. The ColorMod is an abstract class that encapsulates how to translate between pixel values of an image and its red, green, blue, and alpha components. This toolkit method is used by the getColorModel method of Component. |
|
getDefaultToolkit() |
Gets the default toolkit. If there is a system property named "awt.toolkit",
that property is treated as the name of a class that is a subclass of Toolkit.
If the system property does not exist, then the default toolkit used is the
class named "sun.awt.motif.MToolkit", which is a motif
implementation of the Abstract Window Toolkit. Returns: the default toolkit.Throws :AWTError, if a toolkit could not be found or could not be
instantiated. |
|
getFontList() |
Returns: the names of
the available fonts in this toolkit. |
|
getFontMetrics(Font font) |
Returns: the screen metrics of the font argument in
this toolkit. |
|
getImage(String filename) |
Returns: an image which
gets its pixel data from the specified file |
|
getImage(URL url) |
Returns: an image which
gets its pixel data from the specified URL. |
|
getScreenResolution() |
Returns: this toolkit's screen resolution in
dots-per-inch. |
|
getScreenSize() |
Returns: the size of
this toolkit's screen in pixels. |
|
prepareImage( ... ) |
Prepares an image for rendering. If the width and height arguments are both -1, this method prepares the image for rendering on the default screen; otherwise, this method prepares an image for rendering on the default screen at the specified width and height. The image data is downloaded asynchronously in another thread and an appropriately scaled screen representation of the image is generated. This toolkit method is used by the prepareImage methods of Component. Information on the flags returned by this method can be found in. Returns:true if the image has already been fully prepared; false otherwise |
|
sync() |
Synchronizes this toolkit's graphics
state. Some window systems may do buffering of graphics events. This method
ensures that the display is up to date. |
A Window is a top-level window; it has no borders and no menubar. It could be used, for example, to implement a pop-up menu. The AWT sends the window all mouse, keyboard, and focus events that occur over it. The default layout for a window is BorderLayout.
public class java.awt.Window extends java.awt.Container
{
// Constructors
public Window(Frame parent);
/* Constructs a new invisible window. The window behaves as a modal dialog in that it will block input to other application windows when shown. Use the show method to cause the window to become visible.
*/
// Methods
public void addNotify();
public void dispose();
public Toolkit getToolkit();
public final String getWarningString();
public void pack();
public void show();
public void toBack();
public void toFront();
}
Table 4.37
|
Method |
Description |
|
addNotify() |
This method calls the createWindow method of this object's toolkit in order to create a WindowPeer for this window. This peer allows the application to change the look of a window without changing its functionality. Most applications do not call this method directly. |
|
dispose() |
Disposes of this window and any resources
used by this window. |
|
getToolkit() |
Determines the toolkit of this window. The implementation of getToolkit in class Window returns the default toolkit . However subclasses of Window can override this method in order to create their own toolkits. Returns: the toolkit of this window. |
|
getWarningString() |
Returns the warning string that is displayed with this window. If this window is insecure, the warning string is displayed somewhere in the visible area of the window. A window is insecure if there is a security manager, and its checkTopLevelWindow method returns false when passed this window as an argument. If the window is secure, then the getWarningString method returns null. If the window is insecure, this methods checks for a system property awt.appletWarning and returns the string value of that property. If there is no such property, the default warning string is used instead. The default warning string is "Warning: Applet Window". Returns: the warning string for this wind |
|
pack() |
Causes the subcomponents of this window to be laid
out at their preferred size. |
|
show() |
If this window is not yet visible, make it visible.
If this window is already visible, then bring it to the front. |
|
toBack() |
Sends this window to the back. |
|
toFront() |
Brings this window to the front. |
The LayoutManager interface specifies the methods that all layout managers must implement. Alayout manager is a class for laying out the components of a Container.
public interface java.awt.LayoutManager
{
// Methods
public abstract void addLayoutComponent(String name, Component comp);
public abstract void layoutContainer(Container parent);
public abstract Dimension minimumLayoutSize(Container parent);
public abstract Dimension preferredLayoutSize(Container parent);
public abstract void removeLayoutComponent(Component comp);
}
Table 4.38
|
Method |
Description |
|
addLayoutComponent( ... ) |
Adds the specified component to this layout using
the indicated
tag. Most applications do not call this method directly. This method
is called when a component is added
to a container using the add(String, Component) method. |
|
layoutContainer( ... ) |
Lays out the container argument using
this layout. This method may reshape
the components in the specified target container in order to satisfy the
constraints of this layout manager.
Most applications do not call this method directly. This method is
called when a container calls its layout method. |
|
minimumLayoutSize( ... ) |
Determines the minimum size of the
container argument using this layout manager. Most applications do not call
this method directly. This method is called when a container calls its layout
method. Returns: the minimum
dimensions needed to lay out the subcomponents of the specified container. |
|
preferredLayoutSize( ... ) |
Determines the preferred size of the
container argument using this layout manager. Most applications do not call
this method directly. This method is called when a container calls its preferredSize
method.Returns:
the preferred dimensions
to lay out the subcomponents of the specified container. |
|
removeLayoutComponent( ...) |
Removes the specified component from this layout.Most applications do not call this method directly. This method is called when a container calls its remove or removeAll methods. |
The MenuContainer interface specifies the methods that all menu-related containers must implement. Note that menu containers are not required to be full-fleged Container objects.
public interface java.awt.MenuContainer
{
// Methods
public abstract Font getFont();
public abstract boolean postEvent(Event evt);
public abstract void remove(MenuComponent comp);
}
Table 4.39
|
Method |
Description |
|
getFont() |
Returns: the font used
in this menu component, if there is one; null otherwise . |
|
postEvent(Event evt) |
Posts an event to this menu container. eturns: true if this menu component
or one of its parents handled the event; false otherwise. |
|
remove(MenuComponent comp) |
Removes the specified menu component from this menu
container. |
Thrown when an Abstract Window Toolkit exception has occurred.
public class java.awt.AWTException extends java.lang.Exception
{
// Constructors
public AWTException(String msg); // Constructs an AWTException with the specified detail message.
}
public class java.awt.AWTError extends java.lang.Error
{
// Constructors
public AWTError(String msg); // Constructs an AWTException with the specified detail message.
}
