问Galaxy Note无法使用MediaPlayer播放声音

EN

MediaPlayer mediaPlayer;

protected class SoundPlayer extends AsyncTask<Integer, Void, Void> {
    @Override
    protected Void doInBackground(Integer... params) {
        mediaPlayer = new MediaPlayer();
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_RING);
        Uri uri = Uri.parse("android.resource://com.example.mediaplayertest/" + params[0]);
        try {
            mediaPlayer.setDataSource(getApplicationContext(), uri);
            mediaPlayer.prepare();
            mediaPlayer.start();
            mediaPlayer.setLooping(false);
        } catch (Exception e) {
            Log.d("MPT", e.getMessage());
        }
        return null;
    }
}   

public void startPlayingSound(View v) {
    soundPlayer = new SoundPlayer();
    try {
        soundPlayer.execute(R.raw.alarm);
    } catch(Exception e) {
        Log.d("MPT", e.getMessage());
    }
}

public void stopPlayingSound(View v) {
    if(mediaPlayer.isPlaying()) {
        mediaPlayer.stop();
    }
}