JLayer - Pause and resume song

问题

I've noticed that a lot of topics were about pausing/resuming an MP3 using JLayer, so in order to help everybody, I've made a whole entire class designed just for that! Please see the answer below.

Note: This was for my personal use, so it may not be as robust as some people were hoping. But it is not that hard to make simple modifications, due to its simplicity.

回答1:

A very simple implementation of a player that is really pausing playback. It works by using a separate thread to play the stream and telling the player thread if/when to pause and resume.

public class PausablePlayer {

    private final static int NOTSTARTED = 0;
    private final static int PLAYING = 1;
    private final static int PAUSED = 2;
    private final static int FINISHED = 3;

    // the player actually doing all the work
    private final Player player;

    // locking object used to communicate with player thread
    private final Object playerLock = new Object();

    // status variable what player thread is doing/supposed to do
    private int playerStatus = NOTSTARTED;

    public PausablePlayer(final InputStream inputStream) throws JavaLayerException {
        this.player = new Player(inputStream);
    }

    public PausablePlayer(final InputStream inputStream, final AudioDevice audioDevice) throws JavaLayerException {
        this.player = new Player(inputStream, audioDevice);
    }

    /**
     * Starts playback (resumes if paused)
     */
    public void play() throws JavaLayerException {
        synchronized (playerLock) {
            switch (playerStatus) {
                case NOTSTARTED:
                    final Runnable r = new Runnable() {
                        public void run() {
                            playInternal();
                        }
                    };
                    final Thread t = new Thread(r);
                    t.setDaemon(true);
                    t.setPriority(Thread.MAX_PRIORITY);
                    playerStatus = PLAYING;
                    t.start();
                    break;
                case PAUSED:
                    resume();
                    break;
                default:
                    break;
            }
        }
    }

    /**
     * Pauses playback. Returns true if new state is PAUSED.
     */
    public boolean pause() {
        synchronized (playerLock) {
            if (playerStatus == PLAYING) {
                playerStatus = PAUSED;
            }
            return playerStatus == PAUSED;
        }
    }

    /**
     * Resumes playback. Returns true if the new state is PLAYING.
     */
    public boolean resume() {
        synchronized (playerLock) {
            if (playerStatus == PAUSED) {
                playerStatus = PLAYING;
                playerLock.notifyAll();
            }
            return playerStatus == PLAYING;
        }
    }

    /**
     * Stops playback. If not playing, does nothing
     */
    public void stop() {
        synchronized (playerLock) {
            playerStatus = FINISHED;
            playerLock.notifyAll();
        }
    }

    private void playInternal() {
        while (playerStatus != FINISHED) {
            try {
                if (!player.play(1)) {
                    break;
                }
            } catch (final JavaLayerException e) {
                break;
            }
            // check if paused or terminated
            synchronized (playerLock) {
                while (playerStatus == PAUSED) {
                    try {
                        playerLock.wait();
                    } catch (final InterruptedException e) {
                        // terminate player
                        break;
                    }
                }
            }
        }
        close();
    }

    /**
     * Closes the player, regardless of current state.
     */
    public void close() {
        synchronized (playerLock) {
            playerStatus = FINISHED;
        }
        try {
            player.close();
        } catch (final Exception e) {
            // ignore, we are terminating anyway
        }
    }

    // demo how to use
    public static void main(String[] argv) {
        try {
            FileInputStream input = new FileInputStream("myfile.mp3"); 
            PausablePlayer player = new PausablePlayer(input);

            // start playing
            player.play();

            // after 5 secs, pause
            Thread.sleep(5000);
            player.pause();     

            // after 5 secs, resume
            Thread.sleep(5000);
            player.resume();
        } catch (final Exception e) {
            throw new RuntimeException(e);
        }
    }

}

回答2:

import java.io.BufferedInputStream;
import java.io.FileInputStream;

import javax.swing.JOptionPane;

import javazoom.jl.player.Player;


public class CustomPlayer {

private Player player;
private FileInputStream FIS;
private BufferedInputStream BIS;
private boolean canResume;
private String path;
private int total;
private int stopped;
private boolean valid;

public CustomPlayer(){
    player = null;
    FIS = null;
    valid = false;
    BIS = null;
    path = null;
    total = 0;
    stopped = 0;
    canResume = false;
}

public boolean canResume(){
    return canResume;
}

public void setPath(String path){
    this.path = path;
}

public void pause(){
    try{
    stopped = FIS.available();
    player.close();
    FIS = null;
    BIS = null;
    player = null;
    if(valid) canResume = true;
    }catch(Exception e){

    }
}

public void resume(){
    if(!canResume) return;
    if(play(total-stopped)) canResume = false;
}

public boolean play(int pos){
    valid = true;
    canResume = false;
    try{
    FIS = new FileInputStream(path);
    total = FIS.available();
    if(pos > -1) FIS.skip(pos);
    BIS = new BufferedInputStream(FIS);
    player = new Player(BIS);
    new Thread(
            new Runnable(){
                public void run(){
                    try{
                        player.play();
                    }catch(Exception e){
                        JOptionPane.showMessageDialog(null, "Error playing mp3 file");
                        valid = false;
                    }
                }
            }
    ).start();
    }catch(Exception e){
        JOptionPane.showMessageDialog(null, "Error playing mp3 file");
        valid = false;
    }
    return valid;
}

}

And for the usage:

CustomPlayer player = new CustomPlayer();
player.setPath("MP3_FILE_PATH");
player.play(-1);

and then when you want to pause it:

player.pause();

...and to resume it:

player.resume();

I hope I've helped a lot of people with this.

回答3:

though this question is some years old now, you should notice that this solution won't work with the newest JLayer version and the AdvancedPlayer!

AdvancedPlayer -> public boolean play(int frames) -> the conditional