Android 音量调节
音量调节在AudioService.java 的借口函数是 adjustStreamVolume 如下:
public void adjustStreamVolume(int streamType, int direction, int flags,
String callingPackage) {
if (mUseFixedVolume) {
return;
}
if (DEBUG_VOL) Log.d(TAG, "adjustStreamVolume() stream="+streamType+", dir="+direction);
ensureValidDirection(direction);
ensureValidStreamType(streamType);
// use stream type alias here so that streams with same alias have the same behavior,
// including with regard to silent mode control (e.g the use of STREAM_RING below and in
// checkForRingerModeChange() in place of STREAM_RING or STREAM_NOTIFICATION)
int streamTypeAlias = mStreamVolumeAlias[streamType];
VolumeStreamState streamState = mStreamStates[streamTypeAlias];
final int device = getDeviceForStream(streamTypeAlias);
int aliasIndex = streamState.getIndex(device);
boolean adjustVolume = true;
int step;
// skip a2dp absolute volume control request when the device
// is not an a2dp device
if ((device & AudioSystem.DEVICE_OUT_ALL_A2DP) == 0 &&
(flags & AudioManager.FLAG_BLUETOOTH_ABS_VOLUME) != 0) {
return;
}
if (mAppOps.noteOp(STEAM_VOLUME_OPS[streamTypeAlias], Binder.getCallingUid(),
callingPackage) != AppOpsManager.MODE_ALLOWED) {
return;
}
// reset any pending volume command
synchronized (mSafeMediaVolumeState) {
mPendingVolumeCommand = null;
}
flags &= ~AudioManager.FLAG_FIXED_VOLUME;
if ((streamTypeAlias == AudioSystem.STREAM_MUSIC) &&
((device & mFixedVolumeDevices) != 0)) {
flags |= AudioManager.FLAG_FIXED_VOLUME;
// Always toggle between max safe volume and 0 for fixed volume devices where safe
// volume is enforced, and max and 0 for the others.
// This is simulated by stepping by the full allowed volume range
if (mSafeMediaVolumeState == SAFE_MEDIA_VOLUME_ACTIVE &&
(device & mSafeMediaVolumeDevices) != 0) {
step = mSafeMediaVolumeIndex;
} else {
step = streamState.getMaxIndex();
}
if (aliasIndex != 0) {
aliasIndex = step;
}
} else {
// convert one UI step (+/-1) into a number of internal units on the stream alias
step = rescaleIndex(10, streamType, streamTypeAlias);
}
// If either the client forces allowing ringer modes for this adjustment,
// or the stream type is one that is affected by ringer modes
if (((flags & AudioManager.FLAG_ALLOW_RINGER_MODES) != 0) ||
(streamTypeAlias == getMasterStreamType())) {
int ringerMode = getRingerMode();
// do not vibrate if already in vibrate mode
if (ringerMode == AudioManager.RINGER_MODE_VIBRATE) {
flags &= ~AudioManager.FLAG_VIBRATE;
}
// Check if the ringer mode changes with this volume adjustment. If
// it does, it will handle adjusting the volume, so we won't below
adjustVolume = checkForRingerModeChange(aliasIndex, direction, step);
}
int oldIndex = mStreamStates[streamType].getIndex(device); 在同一种streamtype 下, 每一个设备都有自己的index
if (adjustVolume && (direction != AudioManager.ADJUST_SAME)) {
// Check if volume update should be send to AVRCP
if (streamTypeAlias == AudioSystem.STREAM_MUSIC &&
(device & AudioSystem.DEVICE_OUT_ALL_A2DP) != 0 &&
(flags & AudioManager.FLAG_BLUETOOTH_ABS_VOLUME) == 0) {
synchronized (mA2dpAvrcpLock) {
if (mA2dp != null && mAvrcpAbsVolSupported) {
mA2dp.adjustAvrcpAbsoluteVolume(direction);
}
}
}
if ((direction == AudioManager.ADJUST_RAISE) &&
!checkSafeMediaVolume(streamTypeAlias, aliasIndex + step, device)) {
Log.e(TAG, "adjustStreamVolume() safe volume index = "+oldIndex);
mVolumePanel.postDisplaySafeVolumeWarning(flags);
} else if (streamState.adjustIndex(direction * step, device)) { 每按一次volume键, 都会调整index , direction 为调整方向, -1 是调低 , +1是调高
// 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_DEVICE_VOLUME,
SENDMSG_QUEUE,
device,
0,
streamState,
0);
}
}
int index = mStreamStates[streamType].getIndex(device); 在同一种streamtype 下, 每一个设备都有自己的index
sendVolumeUpdate(streamType, oldIndex, index, flags);
}
下面分析下这个函数, 主要就是
1. (红色标记部分) 按volume key 都会保存调整index
2. (蓝色标记部分) 根据这个index , 调用到handleMessage 函数中的setDeviceVolume函数, 然后去AudioPolicyManagerBase.cpp 计算音频曲线, 然后在AudioPolicyManagerBase.cpp 中调用 mpClientInterface->setStreamVolume 函数, 把音量设置到AudioFlinger 中去
3. (绿色标记部分) 根据当前case 的streamtype , 和oldindex , index 去更新应用的音量条显示
另外标记紫色的地方是对RINGER_MODE_NORMAL, RINGER_MODE_VIBRATE 和RINGER_MODE_SILENT 进行转换
如果当前case 下的streamTypeAlias 等于getMasterStreamType() , 就会调用checkForRingerModeChange 这个函数,如下
private boolean checkForRingerModeChange(int oldIndex, int direction, int step) {
boolean adjustVolumeIndex = true;
int ringerMode = getRingerMode();
switch (ringerMode) {
case RINGER_MODE_NORMAL:
if (direction == AudioManager.ADJUST_LOWER) {
if (mHasVibrator) {
// "step" is the delta in internal index units corresponding to a
// change of 1 in UI index units.
// Because of rounding when rescaling from one stream index range to its alias
// index range, we cannot simply test oldIndex == step:
// (step <= oldIndex < 2 * step) is equivalent to: (old UI index == 1)
if (step <= oldIndex && oldIndex < 2 * step) {
ringerMode = RINGER_MODE_VIBRATE;
}
} else {
// (oldIndex < step) is equivalent to (old UI index == 0)
if ((oldIndex < step) && mPrevVolDirection != AudioManager.ADJUST_LOWER) {
ringerMode = RINGER_MODE_SILENT;
}
}
}
break;
case RINGER_MODE_VIBRATE:
if (!mHasVibrator) {
Log.e(TAG, "checkForRingerModeChange() current ringer mode is vibrate" +
"but no vibrator is present");
break;
}
if ((direction == AudioManager.ADJUST_LOWER)) {
if (mPrevVolDirection != AudioManager.ADJUST_LOWER) {
ringerMode = RINGER_MODE_SILENT;
}
} else if (direction == AudioManager.ADJUST_RAISE) {
ringerMode = RINGER_MODE_NORMAL;
}
adjustVolumeIndex = false;
break;
case RINGER_MODE_SILENT:
if (direction == AudioManager.ADJUST_RAISE) {
if (mHasVibrator) {
ringerMode = RINGER_MODE_VIBRATE;
} else {
ringerMode = RINGER_MODE_NORMAL;
}
}
adjustVolumeIndex = false;
break;
default:
Log.e(TAG, "checkForRingerModeChange() wrong ringer mode: "+ringerMode);
break;
}
setRingerMode(ringerMode);
mPrevVolDirection = direction;
return adjustVolumeIndex;
}
这个函数绿色标记的地方,是获得和设置Ringer mode .
红色标记的地方, 说明如果音量条调到最低的时候, 就可以转换成振动 , 再到静音了