Android 监听音量键并且改变音量

改变系统的音量，除非涉及到管理各种音量的工具类软件，一般是改变媒体音量，也就是AudioManager.STREAM_MUSIC，比如说打游戏的时候，不能把电话的音量改变了。这样的话需要用到

 private AudioManager audioMgr;

 audioMgr = (AudioManager) getSystemService(Context.AUDIO_SERVICE);

获取最大音量

 maxVolume = audioMgr.getStreamMaxVolume(AudioManager.STREAM_MUSIC);

不同手机的系统最大音量不一样，所以如果需要显示音量变化，需要自己分等份

获取当前音量

 private int getMediaVolume() {        return audioMgr.getStreamVolume(AudioManager.STREAM_MUSIC);    }

设置当前音量

  private void setMediaVolume(int volume) {        audioMgr.setStreamVolume(AudioManager.STREAM_MUSIC, volume, AudioManager.FLAG_PLAY_SOUND);    }

监听音量键事件

 @Override    public boolean onKeyDown(int keyCode, KeyEvent event) {        switch (keyCode) {            case KeyEvent.KEYCODE_VOLUME_UP:                addMediaVolume(getMediaVolume());                playMedia(getMediaVolume());                return true;            case KeyEvent.KEYCODE_VOLUME_DOWN:                cutMediaVolume(getMediaVolume());                playMedia(getMediaVolume());                return true;            default:                break;        }        return super.onKeyDown(keyCode, event);    }

    private void addMediaVolume(int current) {        current = current + stepVolume;        if (current >= maxVolume)            current = maxVolume;        setMediaVolume(current);        volumeSeekBar.setProgress(current);    }    private void cutMediaVolume(int current) {        current = current - stepVolume;        if (current <= 0)            current = 0;        setMediaVolume(current);        volumeSeekBar.setProgress(current);    }

播放

    private void playMedia(int volume) {        if (mediaPlayer != null && mediaPlayer.isPlaying()) {            return;        }        int music = volumeManager.getMusic();        if (music != mMusic) {            mediaPlayer = MediaPlayer.create(getApplicationContext(), music);            mMusic = music;        }        mediaPlayer.start();    }