关于android Master 和 Stream 静音

android中将音量的调节分为全局音量(MasterVolume)和个别音量(StreamVolume)。

    在搞rockchip平台时发现,这两种音量在做静音处理时,行为有所不同。

    StreamVolume在静音后,调节音量大小会从0开始,不会从静音之前的音量开始调节。

    而MasterVolume则能够从静音之前的音量开始。

    如何设置默认使用MasterVolume,还是StreamVolume呢!

    在AudioManager对象中有对静音按键的处理:

        public void handleKeyDown(KeyEvent event, int stream) {
        int keyCode = event.getKeyCode();
        switch (keyCode) {
            case KeyEvent.KEYCODE_VOLUME_UP:
            case KeyEvent.KEYCODE_VOLUME_DOWN:
                /*
                 * Adjust the volume in on key down since it is more
                 * responsive to the user.
                 */
                int flags = FLAG_SHOW_UI | FLAG_VIBRATE;

                if (mUseMasterVolume) {
                    adjustMasterVolume(
                            keyCode == KeyEvent.KEYCODE_VOLUME_UP
                                    ? ADJUST_RAISE
                                    : ADJUST_LOWER,
                            flags);
                } else {
                    adjustSuggestedStreamVolume(
                            keyCode == KeyEvent.KEYCODE_VOLUME_UP
                                    ? ADJUST_RAISE
                                    : ADJUST_LOWER,
                            stream,
                            flags);
                    mVolume = getStreamVolume(STREAM_MUSIC);
                    Log.d(TAG,"mVolume = "+mVolume);
                }
                break;
            case KeyEvent.KEYCODE_VOLUME_MUTE:
                if (event.getRepeatCount() == 0) {
                    if (mUseMasterVolume) {
                        setMasterMute(!isMasterMute());
                    } else {
                        // TODO: Actually handle MUTE.                       
                        if(getStreamVolume(STREAM_MUSIC) != 0)
                        {
                            mVolume = getStreamVolume(STREAM_MUSIC);
                            Log.d(TAG,"mVolume = "+mVolume);
                            setStreamVolume(STREAM_MUSIC, 0, FLAG_SHOW_UI);
                        }
                        else
                        {
                            Log.d(TAG,"mVolume = "+mVolume);
                            setStreamVolume(STREAM_MUSIC, mVolume, FLAG_SHOW_UI);
                        }
                    }
                }
                break;
        }
    }


    mUseMasterVolume控制了使用streamvolume还是mastervolume。

    而mUseMasterVolume是从AudioManager的构造函数中初始化的

    mUseMasterVolume = mContext.getResources().getBoolean(
                com.android.internal.R.bool.config_useMasterVolume);

    com.android.internal.R.bool.config_useMasterVolume又是什么呢?是framework的配置信息。

    可以从frameworks/base/core/res/res下的values/config.xml中找到如下一行:

     false

    把false改为true即可。


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