android -- 蓝牙 bluetooth （五）接电话与听音乐

  1.蓝牙耳机接听电话

        这个就对应HFP（Hands-freeProfile），Free your Hand，蓝牙的初衷之一。先来看这个功能的场景，手机来电，手机与蓝牙耳机已连接，这时会优先触发蓝牙接听电话的代码流程，起步代码在phonesrccomandroidphone CallScreen.java的connectBluetoothAudio() /disconnectBluetoothAudio()，只看连接部分好了，注意下面代码里的注释，

/* package */ void connectBluetoothAudio() {
  if (VDBG) log("connectBluetoothAudio()...");
  if (mBluetoothHeadset != null) {
      // TODO(BT) check return
      mBluetoothHeadset.connectAudio();
  }
  // Watch out: The bluetooth connection doesn't happen instantly;
  // the connectAudio() call returns instantly but does its real
  // work in another thread.  The mBluetoothConnectionPending flag
  // is just a little trickery to ensure that the onscreen UI updates
  // instantly. (See isBluetoothAudioConnectedOrPending() above.)
  mBluetoothConnectionPending = true;
  mBluetoothConnectionRequestTime = SystemClock.elapsedRealtime();

         接下来就跳到蓝牙应用的管辖范围，代码在packages/apps/Bluetooth/src/com/android/bluetooth/hfp/HeadsetService.java，

public boolean connectAudio() {
    HeadsetService service = getService();
    if (service == null) return false;
    return service.connectAudio();
}

        很明显下一个目标是HeadsetService，直接看具体实现，这部分代码跳转都比较清晰，下面代码会先判断当前状态是否正确，关于HeadsetStateMachine几个状态可以参持这个/packages/apps/Bluetooth/src/com/android/bluetooth/hfp/HeadsetStateMachine.java的最前的代码注释。

boolean connectAudio() {
     // TODO(BT) BLUETOOTH or BLUETOOTH_ADMIN permission
     enforceCallingOrSelfPermission(BLUETOOTH_PERM, "Need BLUETOOTH permission");
     if (!mStateMachine.isConnected()) {
         return false;
     }
     if (mStateMachine.isAudioOn()) {
         return false;
     }
     mStateMachine.sendMessage(HeadsetStateMachine.CONNECT_AUDIO);
     return true;
 }

       走进HeadsetStateMachine状态机，找到CONNECT_AUDIO分支，就看带Native的方法connectAudioNative(getByteAddress(mCurrentDevice))；

static jboolean connectAudioNative(JNIEnv *env, jobject object, jbyteArray address) {
    jbyte *addr;
    bt_status_t status;

    if (!sBluetoothHfpInterface) return JNI_FALSE;

    addr = env->GetByteArrayElements(address, NULL);
    if (!addr) {
        jniThrowIOException(env, EINVAL);
        return JNI_FALSE;
    }
//连接在这里
    if ( (status = sBluetoothHfpInterface->connect_audio((bt_bdaddr_t *)addr)) !=
         BT_STATUS_SUCCESS) {
        ALOGE("Failed HF audio connection, status: %d", status);
    }
    env->ReleaseByteArrayElements(address, addr, 0);
    return (status == BT_STATUS_SUCCESS) ? JNI_TRUE : JNI_FALSE;
}

       上面代码还可以进一步跟到下面/external/bluetooth/bluedroid/btif/src/btif_hf.c，到了这里其实流程已经结束了，对于这里消息流转估计要放到以后再写了

static bt_status_t connect_audio( bt_bdaddr_t *bd_addr )
{
    CHECK_BTHF_INIT();
    if (is_connected(bd_addr))
    {
        BTA_AgAudioOpen(btif_hf_cb.handle);
        /* Inform the application that the audio connection has been initiated successfully */
        btif_transfer_context(btif_in_hf_generic_evt, BTIF_HFP_CB_AUDIO_CONNECTING,
                              (char *)bd_addr, sizeof(bt_bdaddr_t), NULL);
        return BT_STATUS_SUCCESS;
    }
    return BT_STATUS_FAIL;
}

 

 2.在蓝牙列表中连接蓝牙耳机

     A2dp的连接过程，在蓝牙搜索结果列表连接一个蓝牙耳机，既然是从设备列表开始，所以起步代码自然是这个了

DevicePickerFragment.java (settingssrccomandroidsettingsluetooth)     3884     2013-6-26
    void onClicked() {
      int bondState = mCachedDevice.getBondState();
      if (mCachedDevice.isConnected()) {
          askDisconnect();
      } else if (bondState == BluetoothDevice.BOND_BONDED) {
          mCachedDevice.connect(true);
      } .......
  }

    void connect(boolean connectAllProfiles) {
      if (!ensurePaired()) {  //要先确保配对
          return;
      }
      mConnectAttempted = SystemClock.elapsedRealtime();
      connectWithoutResettingTimer(connectAllProfiles);//没别的了，只能看到这里
  }

      代码路径这里packages/apps/Settings/src/com/android/settings/bluetooth/CachedBluetoothDevice.java，具体代码看下面

// Try to initialize the profiles if they were not.
     ...........
      // Reset the only-show-one-error-dialog tracking variable
      mIsConnectingErrorPossible = true;

      int preferredProfiles = 0;
      for (LocalBluetoothProfile profile : mProfiles) {
          if (connectAllProfiles ? profile.isConnectable() : profile.isAutoConnectable()) {
              if (profile.isPreferred(mDevice)) {
                  ++preferredProfiles;
                  connectInt(profile);//连接在这里，
              }
          }
      }
     .............

       connectInt的实现很简单，直接跳过看里面的profile.connect(mDevice)，这里的profile是指A2dpProfile，所以connet()方法的具体实现在

public boolean connect(BluetoothDevice device) {
    if (mService == null) return false;
    List<BluetoothDevice> sinks = getConnectedDevices();
    if (sinks != null) {
        for (BluetoothDevice sink : sinks) {
            mService.disconnect(sink);
    }}
    return mService.connect(device);
}

        下面是 BluetoothA2dp.java (frameworksasecorejavaandroidluetooth)  ，为什么是这样看下这个private BluetoothA2dp mService;就知道了

public boolean connect(BluetoothDevice device) {
      if (mService != null && isEnabled() &&
          isValidDevice(device)) {
          try {
              return mService.connect(device);
          } catch (RemoteException e) {
              Log.e(TAG, "Stack:" + Log.getStackTraceString(new Throwable()));
              return false;
          }
      }...........
      return false;

      Binder跳转
      public boolean connect(BluetoothDevice device) {
          A2dpService service = getService();
          if (service == null) return false;
          return service.connect(device);
      }

  }

        之后的跳转和第一部分蓝牙接听电话跳转过程类似，就不重复了，最后会来到packages/apps/Bluetooth/jni/com_android_bluetooth_a2dp.cpp的connectA2dpNative，同样到下面的代码，我们能看到的开放的代码也就是这些，再下面要看vendor的具体实现了。

static jboolean connectA2dpNative(JNIEnv *env, jobject object, jbyteArray address) {
  jbyte *addr;
  bt_bdaddr_t * btAddr;
  bt_status_t status;

  ALOGI("%s: sBluetoothA2dpInterface: %p", __FUNCTION__, sBluetoothA2dpInterface);
  if (!sBluetoothA2dpInterface) return JNI_FALSE;

  addr = env->GetByteArrayElements(address, NULL);
  btAddr = (bt_bdaddr_t *) addr;
  if (!addr) {
      jniThrowIOException(env, EINVAL);
      return JNI_FALSE;
  }
  if ((status = sBluetoothA2dpInterface->connect((bt_bdaddr_t *)addr)) != BT_STATUS_SUCCESS) {
      ALOGE("Failed HF connection, status: %d", status);
  }
  env->ReleaseByteArrayElements(address, addr, 0);
  return (status == BT_STATUS_SUCCESS) ? JNI_TRUE : JNI_FALSE;