插入拔掉耳机流程 audio headset

headset->AudioService->AudioSystem->AudioPolicyManager->AudioFlinger->AudioHWInterface->Driver

AudioService.java    AudioServiceBroadcastReceive()->onReceive()->Intent.ACTION_HEADSET_PLUG->AudioSystem.setDeviceConnectionState()
AudioSystem.java     setDeviceConnectionState()
Android_media_AudioSystem.cpp  android_media_AudioSystem_setDeviceConnectionState()
AudioSystem.cpp     setDeviceConnectionState()
AudioPolicyService.cpp   setDeviceConnectionState()
AudioPolicyManagerBase.cpp   setDeviceConnectionState()->getDeviceForStrategy()->setOutputDevice() 

1.systemserver.java

2.android_server_SystemServer_init1.cpp 

3.System_init.cpp 

4.systemserver.java

新建线程

class ServerThread extends Thread 

{ 

…… 

public void run() 

{ 

…… 

try { 

Log.i(TAG, "Headset Observer"); 

// Listen for wired headset changes 

headset = new HeadsetObserver(context); // new a thread to observer headset status 

} catch (Throwable e) { 

Log.e(TAG, "Failure starting HeadsetObserver", e); 

} 

} 

} 

5.启动服务并广播：HeadsetObserver.java 

class HeadsetObserver extends UeventObserver 

{ 

…… 

public HeadsetObserver(Context context) 

{ 

…… 

startObserving(HEADSET_UEVENT_MATCH); 

init(); // set initial status 

} 

} 

6.AudioService.java中将接收广播

private class AudioServiceBroadcastReceiver extends BroadcastReceiver 

{ 

public void onReceive(Context context, Intent intent) 

{ 

…… 

else if (action.equals(Intent.ACTION_HEADSET_PLUG)) 

{ 

…… 

//if you first insert headset, will implement fellow code 

AudioSystem.setDeviceConnectionState(AudioSystem.DEVICE_OUT_WIRED_HEADSET,AudioSystem.DEVICE_STATE_AVAILABLE,""); 

} 

} 

} 

7.设置设备连接1：状态android_media_AudioSystem.cpp

static JNINativeMethod gMethods[] = { 

"setDeviceConnectionState","(IILjava/lang/String;)I",(void*)android_media_AudioSystem_setDeviceConnectionState}, 

}; 

8.设置连接状态2：AudioSystem.cpp

status_t AudioSystem::setDeviceConnectionState(audio_devices device, 

device_connection_state state, const char *device_address) 

{ 

const sp<IAudioPolicyService>& aps = AudioSystem::get_audio_policy_service(); 

if (aps == 0) return PERMISSION_DENIED; 

return aps->setDeviceConnectionState(device, state, device_address); 

} 

9.设置连接状态3：AudioPolicyManager.cpp

status_t

AudioPolicyManager::setDeviceConnectionState(AudioSystem::audio_devices device, 

AudioSystem::device_connection_state state, const char *device_address) 

{ 

…… 

// handle output devices 

if (AudioSystem::isOutputDevice(device)) 

{ 

switch (state) 

{ 

case AudioSystem::DEVICE_STATE_AVAILABLE: 

…… 

if (AudioSystem::isBluetoothScoDevice(device)) 

{ 

…… 

} 

else if (device == AudioSystem::DEVICE_OUT_WIRED_HEADSET || 

device == AudioSystem::DEVICE_OUT_WIRED_HEADPHONE) 

{ 

if (getDeviceForStrategy(STRATEGY_PHONE) == device && 

(mPhoneState == AudioSystem::MODE_IN_CALL || 

mOutputs.valueFor(mHardwareOutput)->isUsedByStrategy(STRATEGY_PHONE))) 

{ 

newDevice = device; 

} 

else if ((getDeviceForStrategy(STRATEGY_SONIFICATION) & device) && 

mOutputs.valueFor(mHardwareOutput)->isUsedByStrategy(STRATEGY_SONIFICATION)) 

{ 

newDevice = getDeviceForStrategy(STRATEGY_SONIFICATION); 

} 

else if ((getDeviceForStrategy(STRATEGY_MEDIA) == device) && 

mOutputs.valueFor(mHardwareOutput)->isUsedByStrategy(STRATEGY_MEDIA)) 

{ 

newDevice = device; 

} 

else if (getDeviceForStrategy(STRATEGY_DTMF) == device && 

mOutputs.valueFor(mHardwareOutput)->isUsedByStrategy(STRATEGY_DTMF)) 

{ 

newDevice = device; 

} 

} 

} 

} 

10.确定输出设备AudioPolicyManager.cpp

setOutputDevice(mHardwareOutput, newDevice); 

11.最后通过alsa切换通路输出

alsa_default.cpp