MediaPlayer.prepare() throws IllegalStateException on Android L

问题

I have code that plays mp3 file from assets directory:

MediaPlayer mediaPlayer = new MediaPlayer();
descriptor = context.getAssets().openFd("beep.mp3");
mediaPlayer.setDataSource(descriptor.getFileDescriptor(), descriptor.getStartOffset(), descriptor.getLength());
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
mediaPlayer.setVolume(soundLevel, soundLevel);
descriptor.close();
mediaPlayer.setLooping(false);
mediaPlayer.prepare();
mediaPlayer.start();

This code was working fine on every device and every Android version. Until after Android L preview came available. mediaPlayer.prepare();throws IllegalStateException on Nexus 5 running Android L.

Emulator version of Android L works completely fine, I don't own Nexus 5 so can't say what exactly is causing the issue. I am thinking about descriptor.close() line before prepare() called, but not sure.

回答1:

public void myBeep() {
    try {
        if (m.isPlaying()) {
            m.stop();
            m.release();
            m = new MediaPlayer();
        }

        AssetFileDescriptor descriptor = getAssets().openFd("beep.mp3");
        m.setDataSource(descriptor.getFileDescriptor(), descriptor.getStartOffset(), descriptor.getLength());
        descriptor.close();

        m.prepare();
        m.setVolume(1f, 1f);
        m.setLooping(true);
        m.start();
    } catch (Exception e) {
        e.printStackTrace();
    }
};

来源：https://stackoverflow.com/questions/25189539/mediaplayer-prepare-throws-illegalstateexception-on-android-l