applet.java

applet 小程序 提供给大家学习参考

     * <code>URL</code> argument.
     * <p>
     * This method always returns immediately, whether or not the audio
     * clip exists. When this applet attempts to play the audio clip, the
     * data will be loaded.
     *
     * @param   url  an absolute URL giving the location of the audio clip.
     * @return  the audio clip at the specified URL.
     * @see     java.applet.AudioClip
     */
    public AudioClip getAudioClip(URL url) {
	return getAppletContext().getAudioClip(url);
    }

    /**
     * Returns the <code>AudioClip</code> object specified by the
     * <code>URL</code> and <code>name</code> arguments.
     * <p>
     * This method always returns immediately, whether or not the audio
     * clip exists. When this applet attempts to play the audio clip, the
     * data will be loaded.
     *
     * @param   url    an absolute URL giving the base location of the
     *                 audio clip.
     * @param   name   the location of the audio clip, relative to the
     *                 <code>url</code> argument.
     * @return  the audio clip at the specified URL.
     * @see     java.applet.AudioClip
     */
    public AudioClip getAudioClip(URL url, String name) {
	try {
	    return getAudioClip(new URL(url, name));
	} catch (MalformedURLException e) {
	    return null;
	}
    }

    /**
     * Returns information about this applet. An applet should override
     * this method to return a <code>String</code> containing information
     * about the author, version, and copyright of the applet.
     * <p>
     * The implementation of this method provided by the
     * <code>Applet</code> class returns <code>null</code>.
     *
     * @return  a string containing information about the author, version, and
     *          copyright of the applet.
     */
    public String getAppletInfo() {
	return null;
    }

    /**
     * Gets the Locale for the applet, if it has been set.
     * If no Locale has been set, then the default Locale
     * is returned.
     *
     * @return  the Locale for the applet
     * @since   JDK1.1
     */

    public Locale getLocale() {
      Locale locale = super.getLocale();
      if (locale == null) {
	return Locale.getDefault();
      }
      return locale;
    }

    /**
     * Returns information about the parameters that are understood by
     * this applet. An applet should override this method to return an
     * array of <code>Strings</code> describing these parameters.
     * <p>
     * Each element of the array should be a set of three
     * <code>Strings</code> containing the name, the type, and a
     * description. For example:
     * <p><blockquote><pre>
     * String pinfo[][] = {
     *	 {"fps",    "1-10",    "frames per second"},
     *	 {"repeat", "boolean", "repeat image loop"},
     *	 {"imgs",   "url",     "images directory"}
     * };
     * </pre></blockquote>
     * <p>
     * The implementation of this method provided by the
     * <code>Applet</code> class returns <code>null</code>.
     *
     * @return  an array describing the parameters this applet looks for.
     */
    public String[][] getParameterInfo() {
	return null;
    }

    /**
     * Plays the audio clip at the specified absolute URL. Nothing
     * happens if the audio clip cannot be found.
     *
     * @param   url   an absolute URL giving the location of the audio clip.
     */
    public void play(URL url) {
	AudioClip clip = getAudioClip(url);
	if (clip != null) {
	    clip.play();
	}
    }

    /**
     * Plays the audio clip given the URL and a specifier that is
     * relative to it. Nothing happens if the audio clip cannot be found.
     *
     * @param   url    an absolute URL giving the base location of the
     *                 audio clip.
     * @param   name   the location of the audio clip, relative to the
     *                 <code>url</code> argument.
     */
    public void play(URL url, String name) {
	AudioClip clip = getAudioClip(url, name);
	if (clip != null) {
	    clip.play();
	}
    }

    /**
     * Called by the browser or applet viewer to inform
     * this applet that it has been loaded into the system. It is always
     * called before the first time that the <code>start</code> method is
     * called.
     * <p>
     * A subclass of <code>Applet</code> should override this method if
     * it has initialization to perform. For example, an applet with
     * threads would use the <code>init</code> method to create the
     * threads and the <code>destroy</code> method to kill them.
     * <p>
     * The implementation of this method provided by the
     * <code>Applet</code> class does nothing.
     *
     * @see     java.applet.Applet#destroy()
     * @see     java.applet.Applet#start()
     * @see     java.applet.Applet#stop()
     */
    public void init() {
    }

    /**
     * Called by the browser or applet viewer to inform
     * this applet that it should start its execution. It is called after
     * the <code>init</code> method and each time the applet is revisited
     * in a Web page.
     * <p>
     * A subclass of <code>Applet</code> should override this method if
     * it has any operation that it wants to perform each time the Web
     * page containing it is visited. For example, an applet with
     * animation might want to use the <code>start</code> method to
     * resume animation, and the <code>stop</code> method to suspend the
     * animation.
     * <p>
     * Note: some methods, such as <code>getLocationOnScreen</code>, can only
     * provide meaningful results if the applet is showing.  Because
     * <code>isShowing</code> returns <code>false</code> when the applet's
     * <code>start</code> is first called, methods requiring
     * <code>isShowing</code> to return <code>true</code> should be called from
     * a <code>ComponentListener</code>.
     * <p>
     * The implementation of this method provided by the
     * <code>Applet</code> class does nothing.
     *
     * @see     java.applet.Applet#destroy()
     * @see     java.applet.Applet#init()
     * @see     java.applet.Applet#stop()
     * @see     java.awt.Component#isShowing()
     * @see     java.awt.event.ComponentListener#componentShown(java.awt.event.ComponentEvent)
     */
    public void start() {
    }

    /**
     * Called by the browser or applet viewer to inform
     * this applet that it should stop its execution. It is called when
     * the Web page that contains this applet has been replaced by
     * another page, and also just before the applet is to be destroyed.
     * <p>
     * A subclass of <code>Applet</code> should override this method if
     * it has any operation that it wants to perform each time the Web
     * page containing it is no longer visible. For example, an applet
     * with animation might want to use the <code>start</code> method to
     * resume animation, and the <code>stop</code> method to suspend the
     * animation.
     * <p>
     * The implementation of this method provided by the
     * <code>Applet</code> class does nothing.
     *
     * @see     java.applet.Applet#destroy()
     * @see     java.applet.Applet#init()
     */
    public void stop() {
    }

    /**
     * Called by the browser or applet viewer to inform
     * this applet that it is being reclaimed and that it should destroy
     * any resources that it has allocated. The <code>stop</code> method
     * will always be called before <code>destroy</code>.
     * <p>
     * A subclass of <code>Applet</code> should override this method if
     * it has any operation that it wants to perform before it is
     * destroyed. For example, an applet with threads would use the
     * <code>init</code> method to create the threads and the
     * <code>destroy</code> method to kill them.
     * <p>
     * The implementation of this method provided by the
     * <code>Applet</code> class does nothing.
     *
     * @see     java.applet.Applet#init()
     * @see     java.applet.Applet#start()
     * @see     java.applet.Applet#stop()
     */
    public void destroy() {
    }

    //
    // Accessibility support
    //

    AccessibleContext accessibleContext = null;

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

    /**
     * This class implements accessibility support for the 
     * <code>Applet</code> class.  It provides an implementation of the 
     * Java Accessibility API appropriate to applet user-interface elements.
     */
    protected class AccessibleApplet extends AccessibleAWTPanel {

        private static final long serialVersionUID = 8127374778187708896L;

        /**
         * Get the role of this object.
         *
         * @return an instance of AccessibleRole describing the role of the
         * object
         */
        public AccessibleRole getAccessibleRole() {
            return AccessibleRole.FRAME;
        }

        /**
         * Get the state of this object.
         *
         * @return an instance of AccessibleStateSet containing the current
         * state set of the object
         * @see AccessibleState
         */
        public AccessibleStateSet getAccessibleStateSet() {
            AccessibleStateSet states = super.getAccessibleStateSet();
            states.add(AccessibleState.ACTIVE);
            return states;
        }

    }
}