android 蓝牙hfp server实现简介

首先确认配置文件是否开启hfp profile功能。根据设备的角色（hfp client / hfp server）来配置hfp profile.
profile 配置文件路径：
       alps/packages/apps/Bluetooth/res/values/config.xml
       alps/device/${customer}/${ProjectName}/overlay/packages/apps/Bluetooth/res/values/config.xml 


e.g.  设备的角色定义为hfp server,需做如下配置：
    <bool name="profile_supported_hs_hfp">true</bool>

    <bool name="profile_supported_hfpclient">false</bool>

接下来介绍hfp server的实现，以通过蓝牙耳机激活语音识别为例。hfp1.6 版本已经支持了语音识别的实现。

//HF通过发送AT+BVRA命令给AG来发起激活语音识别应用。语音识别应用安装在AG中。

除了audio的路由、语音识别的激活控制等功能需要用到蓝牙功能，其余都依赖于语音识别应用的实现。

//AG 中的bt stack收到hf发过来的cmd AT+BVRA,调用回调函数处理

external/bluetooth/bluedroid/btif/src/btif_hf.c

static void btif_hf_upstreams_evt(UINT16 event, char* p_param){

.....

        case BTA_AG_AT_BVRA_EVT:
            HAL_CBACK(bt_hf_callbacks, vr_cmd_cb,
                (p_data->val.num == 1) ? BTHF_VR_STATE_STARTED :
                      BTHF_VR_STATE_STOPPED, &btif_hf_cb[idx].connected_bda);
            break;

}

//java层的hfp service在初始化的时候，注册回调

packages/apps/Bluetooth/jni/com_android_bluetooth_hfp.cpp

static bthf_callbacks_t sBluetoothHfpCallbacks = {
    sizeof(sBluetoothHfpCallbacks),
    connection_state_callback,
    audio_state_callback,
    voice_recognition_callback,
    answer_call_callback,
    hangup_call_callback,
    volume_control_callback,
    dial_call_callback,
    dtmf_cmd_callback,
    noice_reduction_callback,
    wbs_callback,
    at_chld_callback,
    at_cnum_callback,
    at_cind_callback,
    at_cops_callback,
    at_clcc_callback,
    unknown_at_callback,
    key_pressed_callback
};

packages/apps/Bluetooth/src/com/android/bluetooth/hfp/HeadsetStateMachine.java

private HeadsetStateMachine(HeadsetService context) {

......

initializeNative(max_hf_connections);

} 

packages/apps/Bluetooth/jni/com_android_bluetooth_hfp.cpp

initializeNative（）{

......

    if ( (status = sBluetoothHfpInterface->init(&sBluetoothHfpCallbacks,
          max_hf_clients)) != BT_STATUS_SUCCESS) {
        ALOGE("Failed to initialize Bluetooth HFP, status: %d", status);
        sBluetoothHfpInterface = NULL;
        return;
    }

}

external/bluetooth/bluedroid/btif/src/btif_hf.c

static bt_status_t init( bthf_callbacks_t* callbacks, int max_hf_clients){

......

bt_hf_callbacks = callbacks;

}

//回调函数（ e.g. voice_recognition_callback）首先通过JNI 调用到java中的函数(onVrStateChanged) 

static void voice_recognition_callback(bthf_vr_state_t state, bt_bdaddr_t* bd_addr) {
......
    sCallbackEnv->SetByteArrayRegion(addr, 0, sizeof(bt_bdaddr_t), (jbyte *) bd_addr);
    sCallbackEnv->CallVoidMethod(mCallbacksObj, method_onVrStateChanged, (jint) state, addr);
    checkAndClearExceptionFromCallback(sCallbackEnv, __FUNCTION__);
    sCallbackEnv->DeleteLocalRef(addr);
}

packages/apps/Bluetooth/src/com/android/bluetooth/hfp/HeadsetStateMachine.java

    private void onVrStateChanged(int state, byte[] address) {
        StackEvent event = new StackEvent(EVENT_TYPE_VR_STATE_CHANGED);
        event.valueInt = state;
        event.device = getDevice(address);
        sendMessage(STACK_EVENT, event);
    }

//java中通过发送intent携带action的方式启动语音识别的app

private void processVrEvent(int state, BluetoothDevice device) {

.....

mService.startActivity(sVoiceCommandIntent);

}

HeadsetStateMachine（）{

......

        if (sVoiceCommandIntent == null) {
            sVoiceCommandIntent = new Intent(Intent.ACTION_VOICE_COMMAND);
            sVoiceCommandIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        }

}