basiccachingcontrol.java

FMJ（freedom media for java)是java视频开发的新选择

package net.sf.fmj.ejmf.toolkit.media;

import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.media.CachingControl;
import javax.media.CachingControlEvent;
import javax.swing.JButton;
import javax.swing.JProgressBar;

/**
 * This class provides a CachingControl for the
 * AbstractController class.  It provides a progress bar to
 * monitor the media download.  Its control Component is simply a
 * button that stops the media download.  Whenever there is a
 * change in this BasicCachingControl, a CachingControlEvent is
 * posted automatically.
 *
 * From the book: Essential JMF, Gordon, Talley (ISBN 0130801046).  Used with permission.
 * 
 * @see        net.sf.fmj.ejmf.toolkit.media.AbstractController
 *
 * @author     Steve Talley & Rob Gordon
 */
public class BasicCachingControl implements CachingControl {
    private final static String PAUSEMESSAGE = "Pause";
    private final static String RESUMEMESSAGE = "Resume";

    private boolean isDownloading;
    private boolean isPaused;
    private long length;
    private long progress;
    private JProgressBar progressBar;
    private JButton pauseButton;
    private AbstractController controller;

    /**
     * Constructs a BasicCachingControl for the given
     * AbstractController.  Uses the length arg to initialize the
     * progress bar.
     *
     * @param      c
     *             The AbstractController from which
     *             CachingControlEvents are posted whenever the
     *             status of this BasicCachingControl changes.
     *
     * @param      length
     *             The length of the media to be downloaded.
     */
    public BasicCachingControl(
        AbstractController c,
        long length)
    {
        controller = c;
        progressBar = new JProgressBar();
        progressBar.setMinimum(0);

        pauseButton = new JButton(PAUSEMESSAGE);

        pauseButton.addActionListener(
            new ActionListener() {
                /**
                 * Stops and deallocates the AbstractController
                 * when the stop button is pushed.
                 */
                public void actionPerformed(ActionEvent e) {
                    String label = pauseButton.getText();

                    if( isPaused() ) {
                        pauseButton.setText(PAUSEMESSAGE);
                        setPaused(false);
                    } else {
                        pauseButton.setText(RESUMEMESSAGE);
                        setPaused(true);
                    }

                    //  Resize button to fit new label
                    pauseButton.getParent().validate();
                }
            }
        );

        reset(length);
        controller.addControl(this);
    }

    /**
     * Sets whether the AbstractController is paused or not.
     *
     * @param      isPaused
     *             boolean indicating whether the media is
     *             paused.
     */
    protected synchronized void setPaused(boolean isPaused) {
        this.isPaused = isPaused;
        notifyAll();
    }

    /**
     * Tells whether the media download is paused or not.
     */
    public boolean isPaused() {
        return isPaused;
    }

    /**
     * Blocks the current thread until the download is not
     * paused.
     */
    public synchronized void blockWhilePaused() {
        while( isPaused ) {
            try {
                wait();
            } catch(InterruptedException e) {} 
        }
    }

    /**
     * Sets whether the AbstractController is downloading or not.
     * Other methods in the BasicCachingControl call this method
     * automatically.
     *
     * @param      isDownloading
     *             boolean indicating whether the media is
     *             downloading.
     */
    public void setDownLoading(boolean isDownloading) {
        this.isDownloading = isDownloading;
        if( isDownloading == false ) {
            setPaused(false);
        }
    }

    /**
     * Resets this BasicCachingControl.  Sets the media length,
     * reinitializes the progress bar, and posts a
     * CachingControlEvent.
     *
     * @param      length
     *             The length of the media.
     */
    public synchronized void reset(long length) {
        this.length = length;

        progress = 0;
        progressBar.setValue(0);

        setContentLength(length);
        setDownLoading(false);
        setPaused(false);

        //  Post CachingControlEvent
        controller.postEvent(
            new CachingControlEvent(controller, this, progress) );
    }

    /**
     * Set the length of the media without reinitializing the
     * progress bar.
     *
     * @param      length
     *             The length of the media.
     */
    public synchronized void setContentLength(long length) {
        this.length = length;
        if( length == LENGTH_UNKNOWN ) {
            progressBar.setMaximum(0);
        } else {
            progressBar.setMaximum((int)length);
        }
    }

    /**
     * Set the current progress of the media download.
     *
     * @param      progress
     *             Number of bytes that have been downloaded.
     */
    public synchronized void setContentProgress(long progress) {
        blockWhilePaused();
        this.progress = progress;
        setDownLoading(progress < length);

        progressBar.setValue((int)progress);

        //  Post CachingControlEvent
        controller.postEvent(
            new CachingControlEvent(controller, this, progress) );

        //  Uncomment following line to slow down download enough
        //  for this CachingControl to be useful
//      try { Thread.sleep(500); } catch( InterruptedException e) {} 
    }

    /**
     * Adds an amount of bytes to the media already downloaded.
     *
     * @param      toAdd
     *             Number of bytes that have been downloaded
     *             since the last time this method or
     *             setContentProgress have been called.
     */
    public void addToProgress(long toAdd) {
        setContentProgress(progress + toAdd);
    }

    /**
     * Indicates that the media is fully downloaded.
     */
    public void setDone() {
        setContentProgress(length);
    }

    ////////////////////////////////////////////////////////
    //
    //  javax.media.CachingControl methods
    //
    ////////////////////////////////////////////////////////

    /**
     * Check whether or not media is being downloaded.
     */
    public boolean isDownloading() {
        return isDownloading;
    }

    /**
     * Get the total number of bytes in the media being
     * downloaded.  Returns LENGTH_UNKNOWN if this information is
     * not available.
     *
     * @return     The media length in bytes, or LENGTH_UNKNOWN.
     */
    public long getContentLength() {
        return length;
    }

    /**
     * Get the total number of bytes of media data that have been
     * downloaded so far.
     *
     * @return     The number of bytes downloaded.
     */
    public long getContentProgress() {
        return progress;
    }

    /**
     * Get a Component for displaying the download progress. 
     *
     * @return     Progress bar GUI Component.
     */
    public Component getProgressBarComponent() {
        return progressBar;
    }

    /**
     * Get a Component that provides additional download control.
     * Returns null if only a progress bar is provided.
     *
     * @return     Download control GUI Component.
     */
    public Component getControlComponent() {
        return pauseButton;
    }
}