Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class JApplet - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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javax.swing
Class JApplet

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--java.awt.Panel
                    |
                    +--java.applet.Applet
                          |
                          +--javax.swing.JApplet

public class JApplet
extends Applet
implements Accessible, RootPaneContainer

An extended version of java.applet.Applet that adds support for interposing input and painting behavior in front of the applets children (see glassPane), support for special children that are managed by a LayeredPane (see rootPane) and for Swing MenuBars.

The JApplet class is slightly incompatible with java.applet.Applet. JApplet contains a JRootPane as it's only child. The contentPane should be the parent of any children of the JApplet. This is different than java.applet.Applet, e.g. to add a child to an an java.applet.Applet you'd write:

       applet.add(child);

However using JApplet you need to add the child to the JApplet's contentPane instead:

       applet.getContentPane().add(child);

The same is true for setting LayoutManagers, removing components, listing children, etc. All these methods should normally be sent to the contentPane() instead of the JApplet itself. The contentPane() will always be non-null. Attempting to set it to null will cause the JApplet to throw an exception. The default contentPane() will have a BorderLayout manager set on it.

Please see the JRootPane documentation for a complete description of the contentPane, glassPane, and layeredPane properties.

For the keyboard keys used by this component in the standard Look and Feel (L&F) renditions, see the JApplet key assignments.

Both Netscape Communicator and Internet Explorer 4.0 unconditionally print an error message to the Java console when an applet attempts to access the AWT system event queue. Swing applets do this once, to check if access is permitted. To prevent the warning message in a production applet one can set a client property called "defeatSystemEventQueueCheck" on the JApplets RootPane to any non null value, e.g:

 JRootPane rp = myJApplet.getRootPane();
 rp.putClientProperty("defeatSystemEventQueueCheck", Boolean.TRUE);

We hope that future versions of the browsers will not have this limitation and we'll be able to retire this hack.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. A future release of Swing will provide support for long term persistence.

See Also:: Serialized Form

Inner Class Summary

protected class JApplet.AccessibleJApplet


Field Summary

protected AccessibleContext accessibleContext


protected JRootPane rootPane


protected boolean rootPaneCheckingEnabled


Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Constructor Summary

JApplet()
          Creates a swing applet instance.

Method Summary

protected void addImpl(Component comp, Object constraints, int index)
          By default, children may not be added directly to a this component, they must be added to its contentPane instead.

protected JRootPane createRootPane()
          Called by the constructor methods to create the default rootPane.

AccessibleContext getAccessibleContext()
          Get the AccessibleContext associated with this JApplet

Container getContentPane()
          Returns the contentPane object for this applet.

Component getGlassPane()
          Returns the glassPane object for this applet.

JMenuBar getJMenuBar()
          Returns the menubar set on this applet.

JLayeredPane getLayeredPane()
          Returns the layeredPane object for this applet.

JRootPane getRootPane()
          Returns the rootPane object for this applet.

protected boolean isRootPaneCheckingEnabled()


protected String paramString()
          Returns a string representation of this JApplet.

protected void processKeyEvent(KeyEvent e)
          Processes key events occurring on this component by dispatching them to any registered KeyListener objects.

void remove(Component comp)
          Removes the specified component from this container.

void setContentPane(Container contentPane)
          Sets the contentPane property.

void setGlassPane(Component glassPane)
          Sets the glassPane property.

void setJMenuBar(JMenuBar menuBar)
          Sets the menubar for this applet.

void setLayeredPane(JLayeredPane layeredPane)
          Sets the layeredPane property.

void setLayout(LayoutManager manager)
          By default the layout of this component may not be set, the layout of its contentPane should be set instead.

protected void setRootPane(JRootPane root)
          Sets the rootPane property.

protected void setRootPaneCheckingEnabled(boolean enabled)
          If true then calls to add() and setLayout() will cause an exception to be thrown.

void update(Graphics g)
          Just calls paint(g).

Methods inherited from class java.applet.Applet

destroy, getAppletContext, getAppletInfo, getAudioClip, getAudioClip, getCodeBase, getDocumentBase, getImage, getImage, getLocale, getParameter, getParameterInfo, init, isActive, newAudioClip, play, play, resize, resize, setStub, showStatus, start, stop

Methods inherited from class java.awt.Panel

addNotify

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getInsets, getLayout, getMaximumSize, getMinimumSize, getPreferredSize, insets, invalidate, isAncestorOf, layout, list, list, locate, minimumSize, paint, paintComponents, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, removeAll, removeContainerListener, removeNotify, setCursor, setFont, validate, validateTree

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addPropertyChangeListener, addPropertyChangeListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, firePropertyChange, getBackground, getBounds, getBounds, getColorModel, getComponentOrientation, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getGraphics, getHeight, getInputContext, getInputMethodRequests, getLocation, getLocation, getLocationOnScreen, getName, getParent, getPeer, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isDisplayable, isDoubleBuffered, isEnabled, isFocusTraversable, isLightweight, isOpaque, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processFocusEvent, processInputMethodEvent, processMouseEvent, processMouseMotionEvent, remove, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, setBackground, setBounds, setBounds, setComponentOrientation, setDropTarget, setEnabled, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

rootPane

protected JRootPane rootPane

See Also:: getRootPane(), setRootPane(javax.swing.JRootPane)

rootPaneCheckingEnabled

protected boolean rootPaneCheckingEnabled

See Also:: isRootPaneCheckingEnabled(), setRootPaneCheckingEnabled(boolean)

accessibleContext

protected AccessibleContext accessibleContext

Constructor Detail

JApplet

public JApplet()

Creates a swing applet instance.

Method Detail

createRootPane

protected JRootPane createRootPane()

Called by the constructor methods to create the default rootPane.

processKeyEvent

protected void processKeyEvent(KeyEvent e)

Description copied from class: Component

Processes key events occurring on this component by dispatching them to any registered KeyListener objects.

This method is not called unless key events are enabled for this component. Key events are enabled when one of the following occurs:

A KeyListener object is registered via addKeyListener.
Key events are enabled via enableEvents.

Overrides:: processKeyEvent in class Component

Tags copied from class: Component

Parameters:: e - the key event.
See Also:: KeyEvent, KeyListener, Component.addKeyListener(java.awt.event.KeyListener), Component.enableEvents(long)

update

public void update(Graphics g)

Just calls paint(g). This method was overridden to prevent an unneccessary call to clear the background.

Overrides:: update in class Container

Tags copied from class: Container

Parameters:: g - the specified Graphics window
See Also:: Component.update(java.awt.Graphics)

setJMenuBar

public void setJMenuBar(JMenuBar menuBar)

Sets the menubar for this applet.

Parameters:: menubar - the menubar being placed in the applet
See Also:: getJMenuBar()

getJMenuBar

public JMenuBar getJMenuBar()

Returns the menubar set on this applet.

See Also:: setJMenuBar(javax.swing.JMenuBar)

isRootPaneCheckingEnabled

protected boolean isRootPaneCheckingEnabled()

Returns:: true if add and setLayout should be checked
See Also:: addImpl(java.awt.Component, java.lang.Object, int), setLayout(java.awt.LayoutManager), setRootPaneCheckingEnabled(boolean)

setRootPaneCheckingEnabled

protected void setRootPaneCheckingEnabled(boolean enabled)

If true then calls to add() and setLayout() will cause an exception to be thrown.

See Also:: addImpl(java.awt.Component, java.lang.Object, int), setLayout(java.awt.LayoutManager), isRootPaneCheckingEnabled()

addImpl

protected void addImpl(Component comp,
                       Object constraints,
                       int index)

By default, children may not be added directly to a this component, they must be added to its contentPane instead. For example:

 thiComponent.getContentPane().add(child)

An attempt to add to directly to this component will cause an runtime exception to be thrown. Subclasses can disable this behavior.

Overrides:: addImpl in class Container

Throws:: Error - if called with rootPaneChecking true
See Also:: setRootPaneCheckingEnabled(boolean)

remove

public void remove(Component comp)

Removes the specified component from this container.

Overrides:: remove in class Container

Parameters:: comp - the component to be removed
See Also:: Container.add(java.awt.Component)

setLayout

public void setLayout(LayoutManager manager)

By default the layout of this component may not be set, the layout of its contentPane should be set instead. For example:

 thiComponent.getContentPane().setLayout(new BorderLayout())

An attempt to set the layout of this component will cause an runtime exception to be thrown. Subclasses can disable this behavior.

Overrides:: setLayout in class Container

Throws:: Error - if called with rootPaneChecking true
See Also:: setRootPaneCheckingEnabled(boolean)

getRootPane

public JRootPane getRootPane()

Returns the rootPane object for this applet.

Specified by:: getRootPane in interface RootPaneContainer

See Also:: setRootPane(javax.swing.JRootPane), RootPaneContainer.getRootPane()

setRootPane

protected void setRootPane(JRootPane root)

Sets the rootPane property. This method is called by the constructor.

Parameters:: root - the rootPane object for this applet
See Also:: getRootPane()

getContentPane

public Container getContentPane()

Returns the contentPane object for this applet.

Specified by:: getContentPane in interface RootPaneContainer

See Also:: setContentPane(java.awt.Container), RootPaneContainer.getContentPane()

setContentPane

public void setContentPane(Container contentPane)

Sets the contentPane property. This method is called by the constructor.

Specified by:: setContentPane in interface RootPaneContainer

Parameters:: contentPane - the contentPane object for this applet
Throws:: IllegalComponentStateException - (a runtime exception) if the content pane parameter is null
See Also:: getContentPane(), RootPaneContainer.setContentPane(java.awt.Container)

getLayeredPane

public JLayeredPane getLayeredPane()

Returns the layeredPane object for this applet.

Specified by:: getLayeredPane in interface RootPaneContainer

Throws:: IllegalComponentStateException - (a runtime exception) if the layered pane parameter is null
See Also:: setLayeredPane(javax.swing.JLayeredPane), RootPaneContainer.getLayeredPane()

setLayeredPane

public void setLayeredPane(JLayeredPane layeredPane)

Sets the layeredPane property. This method is called by the constructor.

Specified by:: setLayeredPane in interface RootPaneContainer

Parameters:: layeredPane - the layeredPane object for this applet
See Also:: getLayeredPane(), RootPaneContainer.setLayeredPane(javax.swing.JLayeredPane)

getGlassPane

public Component getGlassPane()

Returns the glassPane object for this applet.

Specified by:: getGlassPane in interface RootPaneContainer

See Also:: setGlassPane(java.awt.Component), RootPaneContainer.getGlassPane()

setGlassPane

public void setGlassPane(Component glassPane)

Sets the glassPane property. This method is called by the constructor.

Specified by:: setGlassPane in interface RootPaneContainer

Parameters:: glassPane - the glassPane object for this applet
See Also:: getGlassPane(), RootPaneContainer.setGlassPane(java.awt.Component)

paramString

protected String paramString()

Returns a string representation of this JApplet. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.

Overrides:: paramString in class Container

Returns:: a string representation of this JApplet.

getAccessibleContext

public AccessibleContext getAccessibleContext()

Get the AccessibleContext associated with this JApplet

Specified by:: getAccessibleContext in interface Accessible

Returns:: the AccessibleContext of this JApplet