android声音调整源代码分析

From: http://blog.csdn.net/bmj/article/details/8796421
加注： Settings.System.SAFE_HEADSET_VOLUME

android调整音量方法有两种,一种是渐进式,即像手动按音量键一样,一步一步增加或减少,另一种是直接设置音量值.

下面先分析第一种渐进式的：

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

public void adjustStreamVolume (int streamType, int direction, int flags)

am.adjustStreamVolume (AudioManager.STREAM_MUSIC, AudioManager.ADJUST_RAISE, AudioManager.FLAG_SHOW_UI);

解释一下三个参数

第一个streamType是需要调整音量的类型,这里设的是媒体音量,可以是:

STREAM_ALARM 警报

STREAM_MUSIC 音乐回放即媒体音量

STREAM_NOTIFICATION 窗口顶部状态栏Notification,

STREAM_RING 铃声

STREAM_SYSTEM 系统

STREAM_VOICE_CALL 通话

STREAM_DTMF 双音多频,不是很明白什么东西



第二个direction,是调整的方向,增加或减少,可以是:

ADJUST_LOWER 降低音量

ADJUST_RAISE 升高音量

ADJUST_SAME 保持不变,这个主要用于向用户展示当前的音量



第三个flags是一些附加参数,只介绍两个常用的

FLAG_PLAY_SOUND 调整音量时播放声音

FLAG_SHOW_UI 调整时显示音量条,就是按音量键出现的那个

0 表示什么也没有

首先跟进AudioManager的adjustStreamVolume（）方法可以看到如下代码：



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public void adjustStreamVolume(int streamType, int direction, int flags) {

IAudioService service = getService();

try {

service.adjustStreamVolume(streamType, direction, flags);

} catch (RemoteException e) {

Log.e(TAG, "Dead object in adjustStreamVolume", e);

}

}

从代码里面可以看到，这里是调用的AudioService里面的adjustStreamVolume（）方法，而AudioService的实现文件是：AudioService.java，其方法实现如下：



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public void adjustStreamVolume(int streamType, int direction, int flags) {

ensureValidDirection(direction); //数据正确性检查

ensureValidStreamType(streamType); //数据正确性检查

。

。

。

// If stream is muted, adjust last audible index only

int index; //局部变量，保存调整后的音量状态

//进行实际的音量调整，在mAudioHandler里面进行。

if (streamState.muteCount() != 0) {

if (adjustVolume) {

streamState.adjustLastAudibleIndex(direction);

// Post a persist volume msg

sendMsg(mAudioHandler, MSG_PERSIST_VOLUME, streamType,

SENDMSG_REPLACE, 0, 1, streamState, PERSIST_DELAY);

}

index = streamState.mLastAudibleIndex;

} else {

if (adjustVolume && streamState.adjustIndex(direction)) {

// Post message to set system volume (it in turn will post a message

// to persist). Do not change volume if stream is muted.

sendMsg(mAudioHandler, MSG_SET_SYSTEM_VOLUME, STREAM_VOLUME_ALIAS[streamType], SENDMSG_NOOP, 0, 0,

streamState, 0);

}

index = streamState.mIndex;

}



// UI //画UI，即调整音量时出现的那个ProgressBar

mVolumePanel.postVolumeChanged(streamType, flags);

// Broadcast Intent //发送广播，广播音量有改变的系统事件

sendVolumeUpdate(streamType, oldIndex, index);

}

下面先来看看画UI的过程：

跟进VolumePanel，发现这个类是一个handle，在postVolumeChanged（）方法里面有如下代码：

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public void postVolumeChanged(int streamType, int flags) {

if (hasMessages(MSG_VOLUME_CHANGED)) return;

removeMessages(MSG_FREE_RESOURCES);

obtainMessage(MSG_VOLUME_CHANGED, streamType, flags).sendToTarget();

}

这里利用了android里面的消息机制来传递消息。对android的消息机制有所了解的应该知道，这个sendToTarget（）方法实际上最后的Target就是它本身，也就是VolumePanel这个类本身，因此我们去这个Handle的handleMessage（）方法里面查找对于MSG_VOLUME_CHANGED这个类型消息的处理：

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case MSG_VOLUME_CHANGED: {

onVolumeChanged(msg.arg1, msg.arg2);

break;

}

可以看到，后续是在onVolumeChanged（）这个方法里面处理的，其两个参数分别是streamType和flags，其中streamType是要调整的音量类型，而flags是传过来的UI类型。onVolumeChanged（）方法代码如下：

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protected void onVolumeChanged(int streamType, int flags) {





if (LOGD) Log.d(TAG, "onVolumeChanged(streamType: " + streamType + ", flags: " + flags + ")");



//根据flags的不同，来做不同的处理

if ((flags & AudioManager.FLAG_SHOW_UI) != 0) {

onShowVolumeChanged(streamType, flags);//UI显示

}





if ((flags & AudioManager.FLAG_PLAY_SOUND) != 0 && ! mRingIsSilent) {

removeMessages(MSG_PLAY_SOUND);

sendMessageDelayed(obtainMessage(MSG_PLAY_SOUND, streamType, flags), PLAY_SOUND_DELAY);//播放声音

}





if ((flags & AudioManager.FLAG_REMOVE_SOUND_AND_VIBRATE) != 0) {

removeMessages(MSG_PLAY_SOUND);

removeMessages(MSG_VIBRATE);

onStopSounds();//停止播放声音和震动

}





removeMessages(MSG_FREE_RESOURCES);

sendMessageDelayed(obtainMessage(MSG_FREE_RESOURCES), FREE_DELAY);

}

通过代码可以知道，根据传进去的flags不同，有不同的处理，下面就看看onShowVolumeChanged（）方法的处理，也就是ProgressBar的显示：



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protected void onShowVolumeChanged(int streamType, int flags) {

int index = mAudioService.getStreamVolume(streamType);

int message = UNKNOWN_VOLUME_TEXT;

int additionalMessage = 0;

mRingIsSilent = false;





if (LOGD) {

Log.d(TAG, "onShowVolumeChanged(streamType: " + streamType

+ ", flags: " + flags + "), index: " + index);

}





// get max volume for progress bar

int max = mAudioService.getStreamMaxVolume(streamType);





switch (streamType) {





case AudioManager.STREAM_RING: { //铃声的处理

setRingerIcon();

message = RINGTONE_VOLUME_TEXT;

Uri ringuri = RingtoneManager.getActualDefaultRingtoneUri(

mContext, RingtoneManager.TYPE_RINGTONE);

Uri ringTwoUri = RingtoneManager.getActualDefaultRingtoneUri(mContext, RingtoneManager.TYPE_RINGTONE,

PhoneFactory.RAW_PHONE_ID);

if ((ringuri == null) && (ringTwoUri == null)) {

additionalMessage =

//com.android.internal.R.string.volume_music_hint_silent_ringtone_selected;

com.android.internal.R.string.volume_music_hint_sim1_and_sim2_silent_ringtone_selected;

mRingIsSilent = true;

} else if ((ringuri == null) && (ringTwoUri != null)) {

additionalMessage =

com.android.internal.R.string.volume_music_hint_silent_sim1_ringtone_selected;

} else if ((ringuri != null) && (ringTwoUri == null)) {

additionalMessage =

com.android.internal.R.string.volume_music_hint_sim2_silent_ringtone_selected;

}

break;

}





case AudioManager.STREAM_MUSIC: { //音乐声音的处理

message = MUSIC_VOLUME_TEXT;

if (mAudioManager.isBluetoothA2dpOn()) {

additionalMessage =

com.android.internal.R.string.volume_music_hint_playing_through_bluetooth;

setLargeIcon(com.android.internal.R.drawable.ic_volume_bluetooth_ad2p);

} else {

setSmallIcon(index);

}

break;

}





case AudioManager.STREAM_FM: { //FM声音的处理

message = FM_VOLUME_TEXT;

setSmallIcon(index);

break;

}





case AudioManager.STREAM_VOICE_CALL: { //通话声音的处理

/*

* For in-call voice call volume, there is no inaudible volume.

* Rescale the UI control so the progress bar doesn't go all

* the way to zero and don't show the mute icon.

*/

index++;

max++;

message = INCALL_VOLUME_TEXT;

setSmallIcon(index);

break;

}





case AudioManager.STREAM_ALARM: { //闹钟声音的处理

message = ALARM_VOLUME_TEXT;

setSmallIcon(index);

break;

}





case AudioManager.STREAM_NOTIFICATION: { //Notification声音的处理

message = NOTIFICATION_VOLUME_TEXT;

setSmallIcon(index);

Uri ringuri = RingtoneManager.getActualDefaultRingtoneUri(

mContext, RingtoneManager.TYPE_NOTIFICATION);

if (ringuri == null) {

additionalMessage =

com.android.internal.R.string.volume_music_hint_silent_ringtone_selected;

mRingIsSilent = true;

}

break;

}





case AudioManager.STREAM_BLUETOOTH_SCO: { //蓝牙_sco？不知道是什么东西。。

/*

* For in-call voice call volume, there is no inaudible volume.

* Rescale the UI control so the progress bar doesn't go all

* the way to zero and don't show the mute icon.

*/

index++;

max++;

message = BLUETOOTH_INCALL_VOLUME_TEXT;

setLargeIcon(com.android.internal.R.drawable.ic_volume_bluetooth_in_call);

break;

}

}





String messageString = Resources.getSystem().getString(message); //根据调整的声音不同，显示不同的信息

if (!mMessage.getText().equals(messageString)) {

mMessage.setText(messageString);

}





if (additionalMessage == 0) {

mAdditionalMessage.setVisibility(View.GONE);

} else {

mAdditionalMessage.setVisibility(View.VISIBLE);

mAdditionalMessage.setText(Resources.getSystem().getString(additionalMessage));

}





if (max != mLevel.getMax()) {

mLevel.setMax(max);

}

mLevel.setProgress(index); //设置ProgressBar的值





mToast.setView(mView);

mToast.setDuration(Toast.LENGTH_SHORT);

mToast.setGravity(Gravity.TOP, 0, 0);

mToast.show();





// Do a little vibrate if applicable (only when going into vibrate mode)

if ((flags & AudioManager.FLAG_VIBRATE) != 0 &&

mAudioService.isStreamAffectedByRingerMode(streamType) &&

mAudioService.getRingerMode() == AudioManager.RINGER_MODE_VIBRATE &&

mAudioService.shouldVibrate(AudioManager.VIBRATE_TYPE_RINGER)) {

sendMessageDelayed(obtainMessage(MSG_VIBRATE), VIBRATE_DELAY);

}

}

在通话声音的处理中，有个setSmallIcon（）函数，可以看到，这个是根据不同情况选择ProgressBar上面显示的图片的。

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private void setSmallIcon(int index) {

mLargeStreamIcon.setVisibility(View.GONE);

mSmallStreamIcon.setVisibility(View.VISIBLE);





mSmallStreamIcon.setImageResource(index == 0

? com.android.internal.R.drawable.ic_volume_off_small

: com.android.internal.R.drawable.ic_volume_small);

}

View view = mView = inflater.inflate(com.android.internal.R.layout.volume_adjust, null);

mLevel就是显示的那个ProgressBar,mLevel = (ProgressBar) view.findViewById(com.android.internal.R.id.level);

从这里我们可以看到，声音调整显示的布局文件是volume_adjust.xml，如果想自己对声音显示的布局进行调整的话，就可以自己手动修改这个布局文件，达到自己想要的效果了。

到这里就把声音调整的UI显示过程分析完了，下面接着来分析声音调整广播发送sendVolumeUpdate（）：



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private void sendVolumeUpdate(int streamType, int oldIndex, int index) {

oldIndex = (oldIndex + 5) / 10;

index = (index + 5) / 10;





Intent intent = new Intent(AudioManager.VOLUME_CHANGED_ACTION);

intent.putExtra(AudioManager.EXTRA_VOLUME_STREAM_TYPE, streamType);

intent.putExtra(AudioManager.EXTRA_VOLUME_STREAM_VALUE, index);

intent.putExtra(AudioManager.EXTRA_PREV_VOLUME_STREAM_VALUE, oldIndex);





mContext.sendBroadcast(intent);

}

可以看到，这里发送了一个广播，而广播的内容是：VOLUME_CHANGED_ACTION，也即"android.media.VOLUME_CHANGED_ACTION";当对音量改变事件有兴趣时，就可以接收这个广播，并做出相应的处理。至此，声音调整的相关流程就分析的差不多了。