private AssetManager assetManager;
    private MediaPlayer playRing() {
        MediaPlayer player = null;
        try {
            player = new MediaPlayer();
            assetManager = getAssets();
            AssetFileDescriptor fileDescriptor = assetManager.openFd("一萬次悲傷.mp3");
            player.setDataSource(fileDescriptor.getFileDescriptor(),fileDescriptor.getStartOffset(),
             fileDescriptor.getStartOffset());
            player.prepare();
            player.start();

        } catch
 
 (IOException e) {
            e.printStackTrace();
        }
        return player;
    }