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JApplet.javaAPI DocJava SE 5 API14593Fri Aug 26 14:57:54 BST 2005javax.swing

JApplet.java

/*
 * @(#)JApplet.java	1.65 03/12/19
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package javax.swing;

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
import java.beans.PropertyChangeListener;
import java.util.Locale;
import java.util.Vector;
import java.io.Serializable;
import javax.accessibility.*;

/**
 * An extended version of <code>java.applet.Applet</code> that adds support for 
 * the JFC/Swing component architecture.
 * You can find task-oriented documentation about using <code>JApplet</code>
 * in <em>The Java Tutorial</em>,
 * in the section 
 * <a
 href="http://java.sun.com/docs/books/tutorial/uiswing/components/applet.html">How to Make Applets</a>.
 * <p>
 * The <code>JApplet</code> class is slightly incompatible with
 * <code>java.applet.Applet</code>.  <code>JApplet</code> contains a
 * <code>JRootPane</code> as its only child.  The <code>contentPane</code>
 * should be the parent of any children of the <code>JApplet</code>.
 * As a convenience <code>add</code> and its variants, <code>remove</code> and
 * <code>setLayout</code> have been overridden to forward to the
 * <code>contentPane</code> as necessary. This means you can write:
 * <pre>
 *       applet.add(child);
 * </pre>
 *
 * And the child will be added to the <code>contentPane</code>.
 * The <code>contentPane</code> will always be non-<code>null</code>.
 * Attempting to set it to <code>null</code> will cause the
 * <code>JApplet</code> to throw an exception. The default
 * <code>contentPane</code> will have a <code>BorderLayout</code>
 * manager set on it. 
 * Refer to {@link javax.swing.RootPaneContainer}
 * for details on adding, removing and setting the <code>LayoutManager</code>
 * of a <code>JApplet</code>.
 * <p>
 * Please see the <code>JRootPane</code> documentation for a
 * complete description of the <code>contentPane</code>, <code>glassPane</code>,
 * and <code>layeredPane</code> properties.
 * <p>
 * <strong>Warning:</strong>
 * 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.  As of 1.4, support for long term storage
 * of all JavaBeans<sup><font size="-2">TM</font></sup>
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @see javax.swing.RootPaneContainer
 * @beaninfo
 *      attribute: isContainer true
 *      attribute: containerDelegate getContentPane
 *    description: Swing's Applet subclass.
 *
 * @version 1.65 12/19/03
 * @author Arnaud Weber
 */
public class JApplet extends Applet implements Accessible, RootPaneContainer 
{
    /**
     * @see #getRootPane
     * @see #setRootPane
     */
    protected JRootPane rootPane;

    /**
     * If true then calls to <code>add</code> and <code>setLayout</code>
     * will be forwarded to the <code>contentPane</code>. This is initially
     * false, but is set to true when the <code>JApplet</code> is constructed.
     *
     * @see #isRootPaneCheckingEnabled
     * @see #setRootPaneCheckingEnabled
     * @see javax.swing.RootPaneContainer
     */
    protected boolean rootPaneCheckingEnabled = false;

    /**
     * Creates a swing applet instance.
     * <p>
     * This constructor sets the component's locale property to the value
     * returned by <code>JComponent.getDefaultLocale</code>. 
     *
     * @exception HeadlessException if GraphicsEnvironment.isHeadless()
     * returns true.
     * @see java.awt.GraphicsEnvironment#isHeadless
     * @see JComponent#getDefaultLocale
     */
    public JApplet() throws HeadlessException {
        super();
	// Check the timerQ and restart if necessary.
	TimerQueue q = TimerQueue.sharedInstance();
	if(q != null) {
	    synchronized(q) {
		if(!q.running)
		    q.start();
	    }
	}

	/* Workaround for bug 4155072.  The shared double buffer image
	 * may hang on to a reference to this applet; unfortunately 
	 * Image.getGraphics() will continue to call JApplet.getForeground()
	 * and getBackground() even after this applet has been destroyed.
	 * So we ensure that these properties are non-null here.
	 */
	setForeground(Color.black);
	setBackground(Color.white);

        setLocale( JComponent.getDefaultLocale() );
        setLayout(new BorderLayout());
        setRootPane(createRootPane());
        setRootPaneCheckingEnabled(true);
	
  	setFocusTraversalPolicyProvider(true);
        sun.awt.SunToolkit.checkAndSetPolicy(this, true);
	
        enableEvents(AWTEvent.KEY_EVENT_MASK);
    }


    /** Called by the constructor methods to create the default rootPane. */
    protected JRootPane createRootPane() {
        JRootPane rp = new JRootPane();
        // NOTE: this uses setOpaque vs LookAndFeel.installProperty as there
        // is NO reason for the RootPane not to be opaque. For painting to
        // work the contentPane must be opaque, therefor the RootPane can
        // also be opaque.
        rp.setOpaque(true);
        return rp;
    }
    
    /** 
     * Just calls <code>paint(g)</code>.  This method was overridden to 
     * prevent an unnecessary call to clear the background.
     */
    public void update(Graphics g) {
        paint(g);
    }


   /**
    * Sets the menubar for this applet.
    * @param menuBar the menubar being placed in the applet
    *
    * @see #getJMenuBar
    *
    * @beaninfo
    *      hidden: true
    * description: The menubar for accessing pulldown menus from this applet.
    */
    public void setJMenuBar(JMenuBar menuBar) {
        getRootPane().setMenuBar(menuBar);
    }

   /**
    * Returns the menubar set on this applet.
    *
    * @see #setJMenuBar
    */
    public JMenuBar getJMenuBar() {
        return getRootPane().getMenuBar();
    }


    /**
     * Returns whether calls to <code>add</code> and 
     * <code>setLayout</code> are forwarded to the <code>contentPane</code>.
     *
     * @return true if <code>add</code> and <code>setLayout</code> 
     *         are fowarded; false otherwise
     *
     * @see #addImpl
     * @see #setLayout
     * @see #setRootPaneCheckingEnabled
     * @see javax.swing.RootPaneContainer
     */
    protected boolean isRootPaneCheckingEnabled() {
        return rootPaneCheckingEnabled;
    }


    /**
     * Sets whether calls to <code>add</code> and 
     * <code>setLayout</code> are forwarded to the <code>contentPane</code>.
     * 
     * @param enabled  true if <code>add</code> and <code>setLayout</code>
     *        are forwarded, false if they should operate directly on the
     *        <code>JApplet</code>.
     *
     * @see #addImpl
     * @see #setLayout
     * @see #isRootPaneCheckingEnabled
     * @see javax.swing.RootPaneContainer
     * @beaninfo
     *      hidden: true
     * description: Whether the add and setLayout methods are forwarded
     */
    protected void setRootPaneCheckingEnabled(boolean enabled) {
        rootPaneCheckingEnabled = enabled;
    }


    /**
     * Adds the specified child <code>Component</code>.
     * This method is overridden to conditionally forwad calls to the
     * <code>contentPane</code>.
     * By default, children are added to the <code>contentPane</code> instead
     * of the frame, refer to {@link javax.swing.RootPaneContainer} for
     * details.
     * 
     * @param comp the component to be enhanced
     * @param constraints the constraints to be respected
     * @param index the index
     * @exception IllegalArgumentException if <code>index</code> is invalid
     * @exception IllegalArgumentException if adding the container's parent
     *			to itself
     * @exception IllegalArgumentException if adding a window to a container
     * 
     * @see #setRootPaneCheckingEnabled
     * @see javax.swing.RootPaneContainer
     */
    protected void addImpl(Component comp, Object constraints, int index) 
    {
        if(isRootPaneCheckingEnabled()) {
            getContentPane().add(comp, constraints, index);
        }
        else {
            super.addImpl(comp, constraints, index);
        }
    }

    /** 
     * Removes the specified component from the container. If
     * <code>comp</code> is not the <code>rootPane</code>, this will forward
     * the call to the <code>contentPane</code>. This will do nothing if
     * <code>comp</code> is not a child of the <code>JFrame</code> or
     * <code>contentPane</code>.
     *
     * @param comp the component to be removed
     * @throws NullPointerException if <code>comp</code> is null
     * @see #add
     * @see javax.swing.RootPaneContainer
     */
    public void remove(Component comp) {
	if (comp == rootPane) {
	    super.remove(comp);
	} else {
	    getContentPane().remove(comp);
	}
    }


    /**
     * Sets the <code>LayoutManager</code>.
     * Overridden to conditionally forward the call to the
     * <code>contentPane</code>.
     * Refer to {@link javax.swing.RootPaneContainer} for
     * more information.
     *
     * @param manager the <code>LayoutManager</code>
     * @see #setRootPaneCheckingEnabled
     * @see javax.swing.RootPaneContainer
     */
    public void setLayout(LayoutManager manager) {
        if(isRootPaneCheckingEnabled()) {
            getContentPane().setLayout(manager);
        }
        else {
            super.setLayout(manager);
        }
    }


    /**
     * Returns the rootPane object for this applet.
     *
     * @see #setRootPane
     * @see RootPaneContainer#getRootPane
     */
    public JRootPane getRootPane() { 
        return rootPane; 
    }


    /**
     * Sets the rootPane property.  This method is called by the constructor.
     * @param root the rootPane object for this applet
     *
     * @see #getRootPane
     *
     * @beaninfo
     *   hidden: true
     * description: the RootPane object for this applet.
     */
    protected void setRootPane(JRootPane root) {
        if(rootPane != null) {
            remove(rootPane);
        }
        rootPane = root;
        if(rootPane != null) {
            boolean checkingEnabled = isRootPaneCheckingEnabled();
            try {
                setRootPaneCheckingEnabled(false);
                add(rootPane, BorderLayout.CENTER);
            }
            finally {
                setRootPaneCheckingEnabled(checkingEnabled);
            }
        }
    }


    /**
     * Returns the contentPane object for this applet.
     *
     * @see #setContentPane
     * @see RootPaneContainer#getContentPane
     */
    public Container getContentPane() { 
        return getRootPane().getContentPane(); 
    }

   /**
     * Sets the contentPane property.  This method is called by the constructor.
     * @param contentPane the contentPane object for this applet
     *
     * @exception java.awt.IllegalComponentStateException (a runtime
     *            exception) if the content pane parameter is null
     * @see #getContentPane
     * @see RootPaneContainer#setContentPane
     *
     * @beaninfo
     *     hidden: true
     *     description: The client area of the applet where child 
     *                  components are normally inserted.
     */
    public void setContentPane(Container contentPane) {
        getRootPane().setContentPane(contentPane);
    }

    /**
     * Returns the layeredPane object for this applet.
     *
     * @exception java.awt.IllegalComponentStateException (a runtime
     *            exception) if the layered pane parameter is null
     * @see #setLayeredPane
     * @see RootPaneContainer#getLayeredPane
     */
    public JLayeredPane getLayeredPane() { 
        return getRootPane().getLayeredPane(); 
    }

    /**
     * Sets the layeredPane property.  This method is called by the constructor.
     * @param layeredPane the layeredPane object for this applet
     *
     * @see #getLayeredPane
     * @see RootPaneContainer#setLayeredPane
     *
     * @beaninfo
     *     hidden: true
     *     description: The pane which holds the various applet layers.
     */
    public void setLayeredPane(JLayeredPane layeredPane) {
        getRootPane().setLayeredPane(layeredPane);
    }

    /**
     * Returns the glassPane object for this applet.
     *
     * @see #setGlassPane
     * @see RootPaneContainer#getGlassPane
     */
    public Component getGlassPane() { 
        return getRootPane().getGlassPane(); 
    }

    /**
     * Sets the glassPane property. 
     * This method is called by the constructor.
     * @param glassPane the glassPane object for this applet
     *
     * @see #getGlassPane
     * @see RootPaneContainer#setGlassPane
     *
     * @beaninfo
     *     hidden: true
     *     description: A transparent pane used for menu rendering.
     */
    public void setGlassPane(Component glassPane) {
        getRootPane().setGlassPane(glassPane);
    }

    /**
     * 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 <code>null</code>.
     * 
     * @return  a string representation of this JApplet.
     */
    protected String paramString() {
	String rootPaneString = (rootPane != null ?
				 rootPane.toString() : "");
	String rootPaneCheckingEnabledString = (rootPaneCheckingEnabled ?
						"true" : "false");

	return super.paramString() +
	",rootPane=" + rootPaneString +
	",rootPaneCheckingEnabled=" + rootPaneCheckingEnabledString;
    }



/////////////////
// Accessibility support
////////////////

    protected AccessibleContext accessibleContext = null;

    /**
     * Gets the AccessibleContext associated with this JApplet. 
     * For JApplets, the AccessibleContext takes the form of an 
     * AccessibleJApplet. 
     * A new AccessibleJApplet instance is created if necessary.
     *
     * @return an AccessibleJApplet that serves as the 
     *         AccessibleContext of this JApplet
     */
    public AccessibleContext getAccessibleContext() {
        if (accessibleContext == null) {
            accessibleContext = new AccessibleJApplet();
        }
        return accessibleContext;
    }

    /**
     * This class implements accessibility support for the 
     * <code>JApplet</code> class.
     */
    protected class AccessibleJApplet extends AccessibleApplet {
        // everything moved to new parent, AccessibleApplet
    }
}