Android藍牙開發【六】hfp鏈接

HFP (Hands-free Profile)，讓藍牙設備（如藍牙耳機）能夠控制電話，如接聽、掛斷、拒接、語音撥號等，拒接、語音撥號要看藍牙耳機及電話是否支持。

HFP定義了音頻網關(AG)和免提組件(HF)兩個角色： 
音頻網關(AG) – 該設備爲音頻（特別是手機）的輸入/輸出網關。 
免提組件(HF) – 該設備做爲音頻網關的遠程音頻輸入/輸出機制，並可提供若干遙控功能。

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2 手機音頻鏈接

對於手機音頻的使用，首先鏈接的藍牙設備須要支持hfp協議，而且須要與該設備進行配對，如何進行藍牙配對這裏就不細說了，能夠參照個人其餘文章。主要分析下其鏈接過程。 
對於系統自帶應用Settings中已配對的藍牙設備界面(以下圖所示)， 

其對應文件路徑： 
packages/apps/Settings/src/com/android/settings/bluetooth/DeviceProfilesSettings.java 
點擊手機音頻進行鏈接，調用onPreferenceChange。

 

1. public boolean onPreferenceChange(Preference preference, Object newValue) {

2. if (preference == mDeviceNamePref) { //重命名

3. mCachedDevice.setName((String) newValue);

4. } else if (preference instanceof CheckBoxPreference) {//check box

5. LocalBluetoothProfile prof = getProfileOf(preference); ／/獲取對應的profile

6. onProfileClicked(prof, (CheckBoxPreference) preference);

7. return false; // checkbox will update from onDeviceAttributesChanged() callback

8. } else {

9. return false;

10. }

11. return true;

12. }

接着看onProfileClicked()函數處理

1. private void onProfileClicked(LocalBluetoothProfile profile, CheckBoxPreference profilePref) {

2. BluetoothDevice device = mCachedDevice.getDevice(); //獲取配對的藍牙設備

3. int status = profile.getConnectionStatus(device); //獲取profile的鏈接狀態

4. boolean isConnected =

5. status == BluetoothProfile.STATE_CONNECTED;

6. if (isConnected) { //若是是鏈接狀態則斷開鏈接

7. askDisconnect(getActivity(), profile);

8. } else { //沒有鏈接

9. if (profile.isPreferred(device)) { //獲取profile是不是首選

10. // profile is preferred but not connected: disable auto-connect

11. profile.setPreferred(device, false); //設置對應profile的PRIORITY 爲off，防止自動鏈接

12. refreshProfilePreference(profilePref, profile); //刷新check box狀態

13. } else {

14. profile.setPreferred(device, true); //設置對應profile的PRIORITY 爲on

15. mCachedDevice.connectProfile(profile); //鏈接指定profile

16. }

17. }

18. }

接着查看CachedBluetoothDevice中的connectProfile函數鏈接某一profile。

1. void connectProfile(LocalBluetoothProfile profile) {

2. mConnectAttempted = SystemClock.elapsedRealtime();

3. // Reset the only-show-one-error-dialog tracking variable

4. mIsConnectingErrorPossible = true;

5. connectInt(profile); //鏈接profile

6. refresh(); // 刷新ui

7. }

8.  

9. synchronized void connectInt(LocalBluetoothProfile profile) {

10. //查看是否配對，若是沒有配對則進行配對，配對後進行鏈接，

11. //若是配對則直接鏈接

12. if (!ensurePaired()) {

13. return;

14. }

15. if (profile.connect(mDevice)) {//鏈接

16. return;

17. }

18. }

connectProfile() ——>connectInt() 
connectInt()函數中會先判斷是否配對，若是沒有配對則開始配對，配對成功後鏈接profile。 
若是已經配對則直接鏈接profile。 
對於profile.connect(mDevice)會根據profile調用各自對應的connect方法。（如手機音頻則對應HeadsetProfile，媒體音頻對應A2dpProfile）。這裏查看手機音頻的鏈接HeadsetProfile。

1. public boolean connect(BluetoothDevice device) {

2. if (mService == null) return false;

3. //獲取鏈接hfp的設備

4. List<BluetoothDevice> sinks = mService.getConnectedDevices();

5. if (sinks != null) {

6. for (BluetoothDevice sink : sinks) {

7. mService.disconnect(sink); //斷開鏈接

8. }

9. } //鏈接hfp。

10. return mService.connect(device);

11. }

HeadsetProfile.java中的connect()方法，mService是經過getProfileProxy獲取的BluetoothHeadset代理對象，經過其進行hfp相關操做。 
mService.connect跳到Bluetooth應用中， 
代碼路徑：packages/apps/Bluetooth/src/com/android/bluetooth/hfp/HeadsetService.java 
先調用到內部類BluetoothHeadsetBinder的connect方法。

1. public boolean connect(BluetoothDevice device) {

2. HeadsetService service = getService();

3. if (service == null) return false;

4. return service.connect(device);

5. }

該方法中很明顯是去調用HeadsetService的connect方法。

 

1. public boolean connect(BluetoothDevice device) {

2. enforceCallingOrSelfPermission(BLUETOOTH_ADMIN_PERM,

3. "Need BLUETOOTH ADMIN permission");

4. if (getPriority(device) == BluetoothProfile.PRIORITY_OFF) {

5. return false; //檢查priority

6. }

7. int connectionState = mStateMachine.getConnectionState(device);

8. if (connectionState == BluetoothProfile.STATE_CONNECTED ||

9. connectionState == BluetoothProfile.STATE_CONNECTING) {

10. return false; //檢查鏈接狀態

11. }

12. mStateMachine.sendMessage(HeadsetStateMachine.CONNECT, device);

13. return true;

14. }

HeadsetService的connect()函數會對priority和鏈接狀態進行必要的檢查，不符合條件則返回false。符合條件則向狀態機發送消息HeadsetStateMachine.CONNECT。 
此時HeadsetStateMachine中狀態應該是Disconnected，因此查看Disconnected state中的處理

1. BluetoothDevice device = (BluetoothDevice) message.obj;

2. //發送廣播，正在鏈接hfp

3. broadcastConnectionState(device, BluetoothProfile.STATE_CONNECTING,

4. BluetoothProfile.STATE_DISCONNECTED);

5. //鏈接遠端設備。

6. if (!connectHfpNative(getByteAddress(device)) ) {

7. //鏈接失敗，向外發送鏈接失敗廣播

8. broadcastConnectionState(device, BluetoothProfile.STATE_DISCONNECTED,

9. BluetoothProfile.STATE_CONNECTING);

10. break;

11. }

12. synchronized (HeadsetStateMachine.this) {

13. mTargetDevice = device;

14. transitionTo(mPending); //切換到pending狀態

15. }

16. sendMessageDelayed(CONNECT_TIMEOUT, 30000);

HeadsetStateMachine調用connectHfpNative()函數來進行手機音頻的鏈接。connectHfpNative是native方法，跳轉到com_android_bluetooth_hfp.cpp中，調用對應的方法connectHfpNative

1. static jboolean connectHfpNative(JNIEnv *env, jobject object, jbyteArray address) {

2. jbyte *addr;

3. bt_status_t status;

4. if (!sBluetoothHfpInterface) return JNI_FALSE;

5. addr = env->GetByteArrayElements(address, NULL);

6. if (!addr) {

7. jniThrowIOException(env, EINVAL);

8. return JNI_FALSE;

9. }

10. if ((status = sBluetoothHfpInterface->connect((bt_bdaddr_t *)addr)) != BT_STATUS_SUCCESS) {

11. ALOGE("Failed HF connection, status: %d", status);

12. }

13. env->ReleaseByteArrayElements(address, addr, 0);

14. return (status == BT_STATUS_SUCCESS) ? JNI_TRUE : JNI_FALSE;

15. }

其中sBluetoothHfpInterface->connect會跳到藍牙協議棧進行鏈接，協議棧就先不進行分析了。

 

3 鏈接狀態

當協議棧鏈接狀態改變會回調com_android_bluetooth_hfp.cpp中的方法connection_state_callback()。

1. static void connection_state_callback(bthf_connection_state_t state, bt_bdaddr_t* bd_addr) {

2. jbyteArray addr;

3. CHECK_CALLBACK_ENV

4. addr = sCallbackEnv->NewByteArray(sizeof(bt_bdaddr_t));

5. if (!addr) {

6. checkAndClearExceptionFromCallback(sCallbackEnv, __FUNCTION__);

7. return;

8. }

9. sCallbackEnv->SetByteArrayRegion(addr, 0, sizeof(bt_bdaddr_t), (jbyte*) bd_addr);

10. sCallbackEnv->CallVoidMethod(mCallbacksObj, method_onConnectionStateChanged,

11. (jint) state, addr);

12. checkAndClearExceptionFromCallback(sCallbackEnv, __FUNCTION__);

13. sCallbackEnv->DeleteLocalRef(addr);

14. }

在connection_state_callback方法中會從cpp層調用到java層，對應於HeadsetStateMachine中的onConnectionStateChanged函數

1. private void onConnectionStateChanged(int state, byte[] address) {

2. StackEvent event = new StackEvent(EVENT_TYPE_CONNECTION_STATE_CHANGED);

3. event.valueInt = state;

4. event.device = getDevice(address);

5. sendMessage(STACK_EVENT, event);

6. }

onConnectionStateChanged函數中發送消息STACK_EVENT（攜帶狀態和藍牙地址），此時是Pending state，收到該消息調用processConnectionEvent。 
正常鏈接成功應該會先收到HeadsetHalConstants.CONNECTION_STATE_CONNECTING狀態，而後收到HeadsetHalConstants.CONNECTION_STATE_CONNECTED狀態。

1. //發送廣播，鏈接成功

2. broadcastConnectionState(mTargetDevice, BluetoothProfile.STATE_CONNECTED,

3. BluetoothProfile.STATE_CONNECTING);

4. synchronized (HeadsetStateMachine.this) {

5. mCurrentDevice = mTargetDevice; //mCurrentDevice表示已鏈接的設備

6. mTargetDevice = null; //mTargetDevice表示要鏈接的設備

7. transitionTo(mConnected); //切換到Connected狀態

8. }

收到HeadsetHalConstants.CONNECTION_STATE_CONNECTED狀態，後向外發送鏈接成功的廣播，狀態機切換到Connected狀態

 

1. private void broadcastConnectionState(BluetoothDevice device, int newState, int prevState) {

2. /* Notifying the connection state change of the profile before sending the intent for

3. connection state change, as it was causing a race condition, with the UI not being

4. updated with the correct connection state. */

5. mService.notifyProfileConnectionStateChanged(device, BluetoothProfile.HEADSET,newState, prevState);

6. Intent intent = new Intent(BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED);

7. intent.putExtra(BluetoothProfile.EXTRA_PREVIOUS_STATE, prevState);

8. intent.putExtra(BluetoothProfile.EXTRA_STATE, newState);

9. intent.putExtra(BluetoothDevice.EXTRA_DEVICE, device);

10. mService.sendBroadcast(intent, HeadsetService.BLUETOOTH_PERM);

11. }

在mService.notifyProfileConnectionStateChanged中會將手機音頻的proirty設置爲auto_connect，而且向外發送BluetoothAdapter.ACTION_CONNECTION_STATE_CHANGED廣播。

在其餘應用中能夠經過廣播接收者註冊BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED該廣播，用來監聽hfp的鏈接狀態。

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4 更新ui

當手機音頻鏈接成功後，Settings應用中會更新ui界面。 
LocalBluetoothProfileManager中會對全部的profile進行管理，其將hfp的profile添加到BluetoothEventManager中，BluetoothEventManager會註冊藍牙狀態改變、各profile狀態改變等廣播。 
當BluetoothEventManager收到BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED廣播後，會根據action獲取對應的handler，調用對應handler的onReceive方法。 
接收到該廣播跳到LocalBluetoothProfileManager內部類StateChangedHandler.onReceive->CachedBluetoothDevice.onProfileStateChanged ->refresh ->dispatchAttributesChanged 
接着跳到DeviceProfilesSettings中的onDeviceAttributesChanged ->refresh.這裏會對界面進行更新，顯示其鏈接狀態信息。

hfp鏈接過程已經分析完了，而斷開鏈接到過程和鏈接總體相差很少，就再也不細說了。