AudioManager audioManager = (AudioManager)getSystemService(Context.AUDIO_SERVICE);
//得到当前声音
int currentVolume = audioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
//得到最大声音值
// 设置音量,4表示设置当前声音大小
audioManager.setStreamVolume(AudioManager.STREAM_MUSIC,4,0);