android声音调整源代码分析（转） _代码分析

花门楼前见秋草，岂能贫贱相看老。这篇文章主要讲述android声音调整源代码分析（转）相关的知识，希望能为你提供帮助。
From: http://blog.csdn.NET/bmj/article/details/8796421
加注： Settings.System.SAFE_HEADSET_VOLUME
【android声音调整源代码分析（转）】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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