android5.0设置模块音量调节流程

最近刚好修改到相关方面的BUG，在这里整理总结一下。

设置中音量相关的Fragment调整到了NotificationSettings.java中。

我们可以在R.xml.notification_settings中看到如下

<!-- Media volume -->
<com.android.settings.notification.VolumeSeekBarPreference
android:key="media_volume"
android:icon="@drawable/ic_audio_vol_24dp"
android:title="@string/media_volume_option_title" />

<!-- Alarm volume -->
<com.android.settings.notification.VolumeSeekBarPreference
android:key="alarm_volume"
android:icon="@drawable/ic_audio_alarm_24dp"
android:title="@string/alarm_volume_option_title" />

<!-- Ring volume -->
<com.android.settings.notification.VolumeSeekBarPreference
android:key="ring_volume"
android:icon="@drawable/ring_notif"
android:title="@string/ring_volume_option_title" />

<!-- Notification volume -->
<com.android.settings.notification.VolumeSeekBarPreference
android:key="notification_volume"
android:icon="@drawable/ring_notif"
android:title="@string/notification_volume_option_title" />

这分别代表多媒体、闹钟、来电铃声和系统通知音量。所以在UI层面上用户是通过调节VolumeSeekBarPreference这个seekbar来最终对系统音量进行调整。

回头看NotificationSettings.java中初始化流程

//sound是包含上面4个SeekBar的PreferenceCategory
final PreferenceCategory sound = (PreferenceCategory) findPreference(KEY_SOUND);
initVolumePreference(KEY_MEDIA_VOLUME, AudioManager.STREAM_MUSIC);
initVolumePreference(KEY_ALARM_VOLUME, AudioManager.STREAM_ALARM);
//判断是否支持通话，支持移除NOTIFICATION_VOLUME否则移除RING_VOLUME
if (mVoiceCapable) {
mRingOrNotificationPreference =
initVolumePreference(KEY_RING_VOLUME, AudioManager.STREAM_RING);
sound.removePreference(sound.findPreference(KEY_NOTIFICATION_VOLUME));
} else {
mRingOrNotificationPreference =
initVolumePreference(KEY_NOTIFICATION_VOLUME, AudioManager.STREAM_NOTIFICATION);
sound.removePreference(sound.findPreference(KEY_RING_VOLUME));
}
initRingtones(sound);

private final VolumePreferenceCallback mVolumeCallback = new VolumePreferenceCallback();

private VolumeSeekBarPreference initVolumePreference(String key, int stream) {
final VolumeSeekBarPreference volumePref = (VolumeSeekBarPreference) findPreference(key);
设置callback
volumePref.setCallback(mVolumeCallback);
//设置AudioManager的stream，可以在AudioSystem中看到具体int值代表的意义
volumePref.setStream(stream);
return volumePref;
}

mVolumeCallback如下，当你拖动seekbar对音量进行调节时这个callback会回馈响应，在界面上进行相应的调整。

private final class VolumePreferenceCallback implements VolumeSeekBarPreference.Callback {
//SeekBarVolumizer是主要负责对系统音量进行调整的类，会在后面描述
private SeekBarVolumizer mCurrent;

@Override
public void onSampleStarting(SeekBarVolumizer sbv) {
if (mCurrent != null && mCurrent != sbv) {
mCurrent.stopSample();
}
mCurrent = sbv;
if (mCurrent != null) {
mHandler.removeMessages(H.STOP_SAMPLE);
mHandler.sendEmptyMessageDelayed(H.STOP_SAMPLE, SAMPLE_CUTOFF);
}
}

@Override
public void onStreamValueChanged(int stream, int progress) {
if (stream == AudioManager.STREAM_RING) {
mHandler.removeMessages(H.UPDATE_RINGER_ICON);
mHandler.obtainMessage(H.UPDATE_RINGER_ICON, progress, 0).sendToTarget();
}
}

public void stopSample() {
if (mCurrent != null) {
mCurrent.stopSample();
}
}
};

@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case UPDATE_PHONE_RINGTONE:
mPhoneRingtonePreference.setSummary((CharSequence) msg.obj);
break;
case UPDATE_NOTIFICATION_RINGTONE:
mNotificationRingtonePreference.setSummary((CharSequence) msg.obj);
break;
case STOP_SAMPLE:
mVolumeCallback.stopSample();
break;
case UPDATE_RINGER_ICON:
updateRingOrNotificationIcon(msg.arg1);
break;
}
}

下面来看VolumeSeekBarPreference.java中可以看到如下代码

private SeekBarVolumizer mVolumizer;
final Uri sampleUri = mStream == AudioManager.STREAM_MUSIC ? getMediaVolumeUri() : null;
if (mVolumizer == null) {
mVolumizer = new SeekBarVolumizer(getContext(), mStream, sampleUri, sbvc) {
// we need to piggyback on SBV's SeekBar listener to update our icon
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromTouch) {
super.onProgressChanged(seekBar, progress, fromTouch);
//这里的mCallback就是VolumePreferenceCallback对象
mCallback.onStreamValueChanged(mStream, progress);
}
};
}
mVolumizer.setSeekBar(mSeekBar);
mIconView = (ImageView) view.findViewById(com.android.internal.R.id.icon);
mCallback.onStreamValueChanged(mStream, mSeekBar.getProgress());

@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromTouch) {
super.onProgressChanged(seekBar, progress, fromTouch);
mCallback.onStreamValueChanged(mStream, progress);
}

这里我们进行下梳理在NotificationSettings.java内initVolumePreference函数的volumePref.setCallback(mVolumeCallback);把VolumePreferenceCallback这个callbak设置到VolumeSeekBarPreference.java内的mCallback中

使得SeekBarVolumizer内的onProgressChanged进行回调时NotificationSettings.java的相应回调函数都响应。

现在看下frameworks/base/core/java/android/preference的SeekBarVolumizer.java

private final Context mContext;
private final Handler mHandler;
private final H mUiHandler = new H();
private final Callback mCallback;
private final Uri mDefaultUri;
private final AudioManager mAudioManager;
private final int mStreamType;
private final int mMaxStreamVolume;
private final Receiver mReceiver = new Receiver();
private final Observer mVolumeObserver;

private int mOriginalStreamVolume;
private Ringtone mRingtone;
private int mLastProgress = -1;
private SeekBar mSeekBar;
private int mVolumeBeforeMute = -1;

private static final int MSG_SET_STREAM_VOLUME = 0;
private static final int MSG_START_SAMPLE = 1;
private static final int MSG_STOP_SAMPLE = 2;
private static final int MSG_INIT_SAMPLE = 3;
private static final int CHECK_RINGTONE_PLAYBACK_DELAY_MS = 1000;

public SeekBarVolumizer(Context context, int streamType, Uri defaultUri,
Callback callback) {
mContext = context;
mAudioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
mStreamType = streamType;
mMaxStreamVolume = mAudioManager.getStreamMaxVolume(mStreamType);
HandlerThread thread = new HandlerThread(TAG + ".CallbackHandler");
thread.start();
mHandler = new Handler(thread.getLooper(), this);
mCallback = callback;
mOriginalStreamVolume = mAudioManager.getStreamVolume(mStreamType);
mVolumeObserver = new Observer(mHandler);
mContext.getContentResolver().registerContentObserver(
System.getUriFor(System.VOLUME_SETTINGS[mStreamType]),
false, mVolumeObserver);
mReceiver.setListening(true);

//mDefaultUri为调整seekbar时听到的调试音
if (defaultUri == null) {
if (mStreamType == AudioManager.STREAM_RING) {
defaultUri = Settings.System.DEFAULT_RINGTONE_URI;
} else if (mStreamType == AudioManager.STREAM_NOTIFICATION) {
defaultUri = Settings.System.DEFAULT_NOTIFICATION_URI;
} else {
defaultUri = Settings.System.DEFAULT_ALARM_ALERT_URI;
}
}
mDefaultUri = defaultUri;
mHandler.sendEmptyMessage(MSG_INIT_SAMPLE);
}

public void setSeekBar(SeekBar seekBar) {
if (mSeekBar != null) {
mSeekBar.setOnSeekBarChangeListener(null);
}
mSeekBar = seekBar;
mSeekBar.setOnSeekBarChangeListener(null);
mSeekBar.setMax(mMaxStreamVolume);
mSeekBar.setProgress(mLastProgress > -1 ? mLastProgress : mOriginalStreamVolume);
mSeekBar.setOnSeekBarChangeListener(this);
}

@Override
public boolean handleMessage(Message msg) {
switch (msg.what) {
//真正调节系统音量的地方
case MSG_SET_STREAM_VOLUME:
mAudioManager.setStreamVolume(mStreamType, mLastProgress,
AudioManager.FLAG_SHOW_UI_WARNINGS);
break;
case MSG_START_SAMPLE:
onStartSample();
break;
case MSG_STOP_SAMPLE:
onStopSample();
break;
case MSG_INIT_SAMPLE:
onInitSample();
break;
default:
Log.e(TAG, "invalid SeekBarVolumizer message: "+msg.what);
}
return true;
}

//初始化mRingtone，我们知道系统播放的铃声最后是通过mRingtone.play()来实现的
private void onInitSample() {
mRingtone = RingtoneManager.getRingtone(mContext, mDefaultUri);
if (mRingtone != null) {
mRingtone.setStreamType(mStreamType);
}
}

private void postStartSample() {
mHandler.removeMessages(MSG_START_SAMPLE);
mHandler.sendMessageDelayed(mHandler.obtainMessage(MSG_START_SAMPLE),
isSamplePlaying() ? CHECK_RINGTONE_PLAYBACK_DELAY_MS : 0);
}

//开始播放调试音
private void onStartSample() {
if (!isSamplePlaying()) {
if (mCallback != null) {
mCallback.onSampleStarting(this);
}
if (mRingtone != null) {
try {
mRingtone.play();
} catch (Throwable e) {
Log.w(TAG, "Error playing ringtone, stream " + mStreamType, e);
}
}
}
}

void postStopSample() {
// remove pending delayed start messages
mHandler.removeMessages(MSG_START_SAMPLE);
mHandler.removeMessages(MSG_STOP_SAMPLE);
mHandler.sendMessage(mHandler.obtainMessage(MSG_STOP_SAMPLE));
}

//停止播放调试音
private void onStopSample() {
if (mRingtone != null) {
mRingtone.stop();
}
}

public void stop() {
postStopSample();
mContext.getContentResolver().unregisterContentObserver(mVolumeObserver);
mSeekBar.setOnSeekBarChangeListener(null);
mReceiver.setListening(false);
mHandler.getLooper().quitSafely();
}

public void revertVolume() {
mAudioManager.setStreamVolume(mStreamType, mOriginalStreamVolume, 0);
}

public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromTouch) {
if (!fromTouch) {
return;
}

postSetVolume(progress);
}

void postSetVolume(int progress) {
// Do the volume changing separately to give responsive UI
mLastProgress = progress;
mHandler.removeMessages(MSG_SET_STREAM_VOLUME);
mHandler.sendMessage(mHandler.obtainMessage(MSG_SET_STREAM_VOLUME));
}

public void onStartTrackingTouch(SeekBar seekBar) {
}

public void onStopTrackingTouch(SeekBar seekBar) {
postStartSample();
}

//判断是否正在播放铃声
public boolean isSamplePlaying() {
return mRingtone != null && mRingtone.isPlaying();
}

public void startSample() {
postStartSample();
}

public void stopSample() {
postStopSample();
}

public SeekBar getSeekBar() {
return mSeekBar;
}

public void changeVolumeBy(int amount) {
mSeekBar.incrementProgressBy(amount);
postSetVolume(mSeekBar.getProgress());
postStartSample();
mVolumeBeforeMute = -1;
}

public void muteVolume() {
if (mVolumeBeforeMute != -1) {
mSeekBar.setProgress(mVolumeBeforeMute);
postSetVolume(mVolumeBeforeMute);
postStartSample();
mVolumeBeforeMute = -1;
} else {
mVolumeBeforeMute = mSeekBar.getProgress();
mSeekBar.setProgress(0);
postStopSample();
postSetVolume(0);
}
}

public void onSaveInstanceState(VolumeStore volumeStore) {
if (mLastProgress >= 0) {
volumeStore.volume = mLastProgress;
volumeStore.originalVolume = mOriginalStreamVolume;
}
}

public void onRestoreInstanceState(VolumeStore volumeStore) {
if (volumeStore.volume != -1) {
mOriginalStreamVolume = volumeStore.originalVolume;
mLastProgress = volumeStore.volume;
postSetVolume(mLastProgress);
}
}

private final class H extends Handler {
private static final int UPDATE_SLIDER = 1;

@Override
public void handleMessage(Message msg) {
if (msg.what == UPDATE_SLIDER) {
if (mSeekBar != null) {
mSeekBar.setProgress(msg.arg1);
mLastProgress = mSeekBar.getProgress();
}
}
}

public void postUpdateSlider(int volume) {
obtainMessage(UPDATE_SLIDER, volume, 0).sendToTarget();
}
}

private final class Observer extends ContentObserver {
public Observer(Handler handler) {
super(handler);
}

@Override
public void onChange(boolean selfChange) {
super.onChange(selfChange);
if (mSeekBar != null && mAudioManager != null) {
final int volume = mAudioManager.getStreamVolume(mStreamType);
mUiHandler.postUpdateSlider(volume);
}
}
}

这里忽视其他所有操作关注一下主要流程，我们知道这个类implements了OnSeekBarChangeListener，这个listener包含了当值发生变化响应的onProgressChanged和开始完成操作的onStartTrackingTouch和onStopTrackingTouch

所以当开始拖动seekbar时onStartTrackingTouch响应无操作，然后onProgressChanged发生变化postSetVolume(progress);从而调用最关键函数mAudioManager.setStreamVolume(mStreamType, mLastProgress,

AudioManager.FLAG_SHOW_UI_WARNINGS);实现音量调整，然后调用onStopTrackingTouch，通过handler调用onStartSample函数来播放调试音，在这过程中通过和setting模块绑定的

callback来对setting模块进行响应，这就时和上层setting模块互动的一个主要流程。