- 播放声音
    - MediaPlayer 播放器, 同时只能播放一个音乐. 可以播放大文件. 播放背景音乐.

            MediaPlayer mediaPlayer = new MediaPlayer();
            mediaPlayer.setDataSource("/mnt/sdcard/bgmusic.mp3");
            mediaPlayer.prepare(); // 准备.
            mediaPlayer.start();

            或

            MediaPlayer mediaPlayer = MediaPlayer.create(MainActivity.this,
                            R.raw.music);
            mediaPlayer.start();

    - SoundPool 声音池, 同时播放多个声音(混合音效). 只允许申请1M的内存空间.

            SoundPool sp = new SoundPool(1, AudioManager.STREAM_MUSIC, 0);
            shoot1id = sp.load("/mnt/sdcard/shoot1.ogg", 1);

            sp.play(shoot1id, 1f, 1f, 0, 0, 1.0f);