AudioManager audioManager = (AudioManager)getSystemService(Context.AUDIO_SERVICE);
//得到當前聲音
int currentVolume = audioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
//得到最大聲音值
// 設置音量,4表示設置當前聲音大小
audioManager.setStreamVolume(AudioManager.STREAM_MUSIC,4,0);