L1 AudioService.adjustSuggestedStreamVolume

前言

AudioService改变音量的方法有几个。实现方式最终的出口AudioSystem.XXX相同，形式上略有不同。

adjustSuggestedStreamVolume

通过物理按键调节，
常见的调用位置是：
http://androidxref.com/5.1.1_r6/xref/frameworks/base/services/core/java/com/android/server/media/MediaSessionService.java#875

boolean isStreamMute = mAudioService.isStreamMute(suggestedStream);
if (direction == MediaSessionManager.DIRECTION_MUTE) {
mAudioManager.setStreamMute(suggestedStream, !isStreamMute);
} else {
mAudioService.adjustSuggestedStreamVolume(direction, suggestedStream,
flags, packageName);
//提到了setStreamMute()的使用
// Do not call setStreamMute when direction = 0 which is used just to
// show the UI.
if (isStreamMute && direction != 0) {
mAudioManager.setStreamMute(suggestedStream, false);
}
}

如果有必要，修改streamType，flags

private void adjustSuggestedStreamVolume(int direction, int suggestedStreamType, int flags,
String callingPackage, int uid) {
if (DEBUG_VOL) Log.d(TAG, "adjustSuggestedStreamVolume() stream="+suggestedStreamType
+ ", flags=" + flags);
int streamType;
if (mVolumeControlStream != -1) {
streamType = mVolumeControlStream;
} else {
// 找到active stream type,就是ringer mode, play music时stream type的原因
streamType = getActiveStreamType(suggestedStreamType);
}
//  找到alias，stream对device的行为，必有这一步

final int resolvedStream = mStreamVolumeAlias[streamType];

// Play sounds on STREAM_RING only.
if ((flags & AudioManager.FLAG_PLAY_SOUND) != 0 &&
resolvedStream != AudioSystem.STREAM_RING) {
flags &= ~AudioManager.FLAG_PLAY_SOUND;
}

// For notifications/ring, show the ui before making any adjustments
if (mVolumeController.suppressAdjustment(resolvedStream, flags)) {
direction = 0;
flags &= ~AudioManager.FLAG_PLAY_SOUND;
flags &= ~AudioManager.FLAG_VIBRATE;
if (DEBUG_VOL) Log.d(TAG, "Volume controller suppressed adjustment");
}

adjustStreamVolume(streamType, direction, flags, callingPackage, uid);
}

相关函数

adjustStreamVolume

adjustStreamVolume可以参考 (L1)AudioService adjustStreamVolume代码走读  点击打开链接

getActiveStreamType

按手机一般调节音量的流程来看
1.  先区分platform------->看到这种if ...else...多的代码就想用多态
2.  区分in communication
3. 判断suggestStreamType

public static final int USE_DEFAULT_STREAM_TYPE = Integer.MIN_VALUE

http://developer.android.com/reference/android/media/AudioManager.html#USE_DEFAULT_STREAM_TYPE
整个函数：
返回值就bluetooth sco, voice call, music, ring, notification 和suggestdStreamType。看来suggestdStreamType就是用来决定是否进判断的

private int getActiveStreamType(int suggestedStreamType) {
switch (mPlatformType) {
case PLATFORM_VOICE:
if (isInCommunication()) {
if (AudioSystem.getForceUse(AudioSystem.FOR_COMMUNICATION)
== AudioSystem.FORCE_BT_SCO) {
// Log.v(TAG, "getActiveStreamType: Forcing STREAM_BLUETOOTH_SCO...");
return AudioSystem.STREAM_BLUETOOTH_SCO;
} else {
// Log.v(TAG, "getActiveStreamType: Forcing STREAM_VOICE_CALL...");
return AudioSystem.STREAM_VOICE_CALL;
}
} else if (suggestedStreamType == AudioManager.USE_DEFAULT_STREAM_TYPE) {
if (isAfMusicActiveRecently(StreamOverride.sDelayMs)) {
if (DEBUG_VOL)
Log.v(TAG, "getActiveStreamType: Forcing STREAM_MUSIC stream active");
return AudioSystem.STREAM_MUSIC;
} else {
if (DEBUG_VOL)
Log.v(TAG, "getActiveStreamType: Forcing STREAM_RING b/c default");
return AudioSystem.STREAM_RING;
}
} else if (isAfMusicActiveRecently(0)) {
if (DEBUG_VOL)
Log.v(TAG, "getActiveStreamType: Forcing STREAM_MUSIC stream active");
return AudioSystem.STREAM_MUSIC;
}
break;
case PLATFORM_TELEVISION:
if (suggestedStreamType == AudioManager.USE_DEFAULT_STREAM_TYPE) {
// TV always defaults to STREAM_MUSIC
return AudioSystem.STREAM_MUSIC;
}
break;
default:
if (isInCommunication()) {
if (AudioSystem.getForceUse(AudioSystem.FOR_COMMUNICATION)
== AudioSystem.FORCE_BT_SCO) {
if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: Forcing STREAM_BLUETOOTH_SCO");
return AudioSystem.STREAM_BLUETOOTH_SCO;
} else {
if (DEBUG_VOL)  Log.v(TAG, "getActiveStreamType: Forcing STREAM_VOICE_CALL");
return AudioSystem.STREAM_VOICE_CALL;
}
} else if (AudioSystem.isStreamActive(AudioSystem.STREAM_NOTIFICATION,
StreamOverride.sDelayMs) ||
AudioSystem.isStreamActive(AudioSystem.STREAM_RING,
StreamOverride.sDelayMs)) {
if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: Forcing STREAM_NOTIFICATION");
return AudioSystem.STREAM_NOTIFICATION;
} else if (suggestedStreamType == AudioManager.USE_DEFAULT_STREAM_TYPE) {
if (isAfMusicActiveRecently(StreamOverride.sDelayMs)) {
if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: forcing STREAM_MUSIC");
return AudioSystem.STREAM_MUSIC;
} else {
if (DEBUG_VOL) Log.v(TAG,
"getActiveStreamType: using STREAM_NOTIFICATION as default");
return AudioSystem.STREAM_NOTIFICATION;
}
}
break;
}
if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: Returning suggested type "
+ suggestedStreamType);
return suggestedStreamType;
}

isAfMusicActiveRecently

调用AudioSystem.isStreamActive(),  AudioSystem.isStreamActiveRemotely() 从native获得状态

private boolean isAfMusicActiveRecently(int delay_ms) {
return AudioSystem.isStreamActive(AudioSystem.STREAM_MUSIC, delay_ms)
|| AudioSystem.isStreamActiveRemotely(AudioSystem.STREAM_MUSIC, delay_ms);
}