android 调整系统内音量

直接上代码：

AudioManager audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
audioManager.setStreamVolume(AudioManager.STREAM_SYSTEM,                 
      audioManager.getStreamMaxVolume(AudioManager.STREAM_SYSTEM), 
      AudioManager.FLAG_SHOW_UI);
audioManager.setStreamVolume(AudioManager.STREAM_MUSIC, 
      audioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC), 
      AudioManager.FLAG_SHOW_UI);
audioManager.setStreamVolume(AudioManager.STREAM_ALARM, 
      audioManager.getStreamMaxVolume(AudioManager.STREAM_ALARM), 
      AudioManager.FLAG_SHOW_UI);