Song plays first time but does not play once stopped : Clip in Java

问题

I am using Clip in java to play a song as follows:

        MR.clip= (Clip) AudioSystem.getLine(MR.info[docIdOfSelectedSong]);
        MR.clip.open(MR.sounds[docIdOfSelectedSong]);
        MR.clip.setMicrosecondPosition(5* 1000000);
        MR.clip.start();

where MR.sounds is an array of type AudioInputStream and MR.info is an array of type DataLine.info. When I press a button ,the above code is called to play the song. Moreover, I have another button to stop the song which calls the below code

public static void stopSong(){

    MR.clip.close();

}

The problem is that when I play the song for the first time, the play and stop button are working fine. But, when I try to play the song for the second time, I cannot hear the song. Any suggestions on what is going wrong?

回答1:

Like all other InputStreams, AudioInputStream can only be read once (unless it can be .reset()). You could try calling .reset() on the AudioInputStream before attemping to play the sound again, but AudioInputStream may not support .reset(). InputStreams are not required to support reset. Also see markSupported().

If .reset() doesn't work, consider constructing a new AudioInputStream every time you need to start playing.

UPDATE: I made an example of caching sound data in memory and using Clip to play those sounds. This example utilizes AudioInputStream.reset(). So how can that work? In fact, AudioInputStream does supports reset() if and only if its underlying InputStream supports .reset(). So my example creates an AudioInputStream that is backed by a ByteArrayInputStream. Because ByteArrayInputStream supports reset, these cached AudioInputStreams also support .reset(), which allows them to be reused.

Note that if you are going to be playing any one cached sound concurrently, you should probably not cache AudioInputStreams, but rather cache byte[]s and construct an AudioInputStream per-playback. This is because AudioInputStream is stateful, so passing a single instance of it to two concurrently running clips, or resetting a stream while one clip is playing, will result in state conflict.

public class CachedSoundClipTest
{
    static ArrayList<AudioInputStream> cachedSounds = 
        new ArrayList<AudioInputStream>();

    public static void main(String[] args) throws Exception
    {
        File[] audioFiles = new File("/audio_storage_directory").listFiles();
        for (File file : audioFiles)
        {
            AudioInputStream reusableAudioInputStream = 
                createReusableAudioInputStream(file);
            cachedSounds.add(reusableAudioInputStream);
        }

        while(true)
        {
            System.out.println("Press enter to play next clip");
            BufferedReader br = 
                new BufferedReader(new InputStreamReader(System.in));
            br.readLine();
            playCachedSound(0);
        }
    }

    private static void playCachedSound(int i) 
        throws IOException, LineUnavailableException
    {
        AudioInputStream stream = cachedSounds.get(i);
        stream.reset();
        Clip clip = AudioSystem.getClip();
        clip.open(stream);
        clip.start();
    }

    private static AudioInputStream createReusableAudioInputStream(File file) 
        throws IOException, UnsupportedAudioFileException
    {
        AudioInputStream ais = null;
        try
        {
            ais = AudioSystem.getAudioInputStream(file);
            byte[] buffer = new byte[1024 * 32];
            int read = 0;
            ByteArrayOutputStream baos = 
                new ByteArrayOutputStream(buffer.length);
            while ((read = ais.read(buffer, 0, buffer.length)) != -1)
            {
                baos.write(buffer, 0, read);
            }
            AudioInputStream reusableAis = 
                new AudioInputStream(
                        new ByteArrayInputStream(baos.toByteArray()),
                        ais.getFormat(),
                        AudioSystem.NOT_SPECIFIED);
            return reusableAis;
        }
        finally
        {
            if (ais != null)
            {
                ais.close();
            }
        }
    }
}

回答2:

The trick is to reset the current position of the clip to the start.

clip.stop();
clip.setMicrosecondPosition(0);
clip.start();

With this method, it is not necessary to load the same resource multiple times. The clip should only be loaded once and be stored as instance variable or something.

回答3:

In your code example, using a Clip, you should use the stop() method instead of the close() method. Then, when you restart, it will pick up where it left off. If you want to restart from the beginning, then you can use the setMicrosecondPosition() or setFramePosition() to 0, and use start().

See: "Using a Clip" in the tutorial below for more details!

http://docs.oracle.com/javase/tutorial/sound/playing.html

The SourceDataLine can only be used once and can't be reset. Yes?

回答4:

I had a similar problem on OS X, where the clip was sometimes not playing if you tried to stop it while it was playing, then restart it from the beginning. It was fixed by calling flush() right after stop():

if(clip.isActive() || clip.isRunning()) {
    clip.stop();
    clip.flush();
}

Definitely don't use close(), use stop() if you want to be able to play your clip again.

来源：https://stackoverflow.com/questions/9999961/song-plays-first-time-but-does-not-play-once-stopped-clip-in-java

标签

java

audio

clip