1. GATT Service Class Initialization

packages/apps/Bluetooth/src/com/android/bluetooth/gatt/GattService.java

public class GattService extends ProfileService {

    static {
        classInitNative();
    }



    private static native void classInitNative();

packages/apps/Bluetooth/jni/com_android_bluetooth_gatt.cpp

static void classInitNative(JNIEnv* env, jclass clazz) {
  // Client callbacks
  method_onClientRegistered =
      env->GetMethodID(clazz, "onClientRegistered", "(IIJJ)V");
......

  // Server callbacks
  method_onServerRegistered =
      env->GetMethodID(clazz, "onServerRegistered", "(IIJJ)V");
......
}

从以上代码流程可知，classInitNative 用于建立 JNI层函数 和 Java层方法 之间的映射关系，从而达到从 JNI 层调用函数在 Java 层执行方法的目的。

2. GATT Service Super Initialization

ProfileService Initialization

3. GATT Service Object Initialization

packages/apps/Bluetooth/src/com/android/bluetooth/gatt/GattService.java

public class GattService extends ProfileService {
    @Override
    protected boolean start() {
        mExposureNotificationPackage = getString(R.string.exposure_notification_package);
        Settings.Global.putInt(
                getContentResolver(), "bluetooth_sanitized_exposure_notification_supported", 1);
        // 1 GATT 初始化
        initializeNative();
        mAdapter = BluetoothAdapter.getDefaultAdapter();
        // 
        mCompanionManager = ICompanionDeviceManager.Stub.asInterface(
                ServiceManager.getService(Context.COMPANION_DEVICE_SERVICE));
        mAppOps = getSystemService(AppOpsManager.class);

        // 2
        mAdvertiseManager = new AdvertiseManager(this, AdapterService.getAdapterService());
        mAdvertiseManager.start();

        // 3
        mScanManager = new ScanManager(this);
        mScanManager.start();

        // 4
        mPeriodicScanManager = new PeriodicScanManager(AdapterService.getAdapterService());
        mPeriodicScanManager.start();

        // 将本类对象赋值到静态变量上
        setGattService(this);
        return true;
    }
}

3.1 GATT Service initializeNative

packages/apps/Bluetooth/src/com/android/bluetooth/gatt/GattService.java

    private native void initializeNative();

packages/apps/Bluetooth/jni/com_android_bluetooth_gatt.cpp

static const btgatt_interface_t* sGattIf = NULL;



static void initializeNative(JNIEnv* env, jobject object) {

  btIf = getBluetoothInterface();

  sGattIf =
      (btgatt_interface_t*)btIf->get_profile_interface(BT_PROFILE_GATT_ID);

  bt_status_t status = sGattIf->init(&sGattCallbacks);

  mCallbacksObj = env->NewGlobalRef(object);
}

get_profile_interface() 函数初始化系列前文已经分析过，用于获取指定的 profile 的入口。此处不再详述其过程，通过入口调用初始化函数代码如下文所示。

system/bt/btif/src/btif_gatt.cc

static bt_status_t btif_gatt_init(const btgatt_callbacks_t* callbacks) {
  bt_gatt_callbacks = callbacks;
  return BT_STATUS_SUCCESS;
}


static btgatt_interface_t btgattInterface = {
    sizeof(btgattInterface),

    btif_gatt_init,
    btif_gatt_cleanup,

    &btgattClientInterface,
    &btgattServerInterface,
    nullptr,  // filled in btif_gatt_get_interface
    nullptr   // filled in btif_gatt_get_interface
};



const btgatt_interface_t* btif_gatt_get_interface() {
  btgattInterface.scanner = get_ble_scanner_instance();
  btgattInterface.advertiser = get_ble_advertiser_instance();
  return &btgattInterface;
}

GATT 初始化完成，已经可以获取到 scanner 和 advertiser 的入口，并且将回调函数注入到 GATT btif 层。

3.2 AdvertiseManager

packages/apps/Bluetooth/src/com/android/bluetooth/gatt/AdvertiseManager.java

class AdvertiseManager {

    static {
        classInitNative();
    }


    AdvertiseManager(GattService service, AdapterService adapterService) {
        mService = service;
        mAdapterService = adapterService;
    }


    void start() {
        initializeNative();
        HandlerThread thread = new HandlerThread("BluetoothAdvertiseManager");
        thread.start();
        mHandler = new Handler(thread.getLooper());
    }



    private static native void classInitNative();

    private native void initializeNative();

packages/apps/Bluetooth/jni/com_android_bluetooth_gatt.cpp

static JNINativeMethod sAdvertiseMethods[] = {
    {"classInitNative", "()V", (void*)advertiseClassInitNative},
    {"initializeNative", "()V", (void*)advertiseInitializeNative},
......
}



static void advertiseClassInitNative(JNIEnv* env, jclass clazz) {
  method_onAdvertisingSetStarted =
      env->GetMethodID(clazz, "onAdvertisingSetStarted", "(IIII)V");
......
}



static void advertiseInitializeNative(JNIEnv* env, jobject object) {
......
  mAdvertiseCallbacksObj = env->NewGlobalRef(object);
}

3.3 ScanManager

packages/apps/Bluetooth/src/com/android/bluetooth/gatt/ScanManager.java

public class ScanManager {

    ScanManager(GattService service) {
        mRegularScanClients =
                Collections.newSetFromMap(new ConcurrentHashMap<ScanClient, Boolean>());
        mBatchClients = Collections.newSetFromMap(new ConcurrentHashMap<ScanClient, Boolean>());
        mSuspendedScanClients =
                Collections.newSetFromMap(new ConcurrentHashMap<ScanClient, Boolean>());
        mService = service;
        mScanNative = new ScanNative();
        mCurUsedTrackableAdvertisements = 0;
        mDm = (DisplayManager) mService.getSystemService(Context.DISPLAY_SERVICE);
        mActivityManager = (ActivityManager) mService.getSystemService(Context.ACTIVITY_SERVICE);
        mLocationManager = (LocationManager) mService.getSystemService(Context.LOCATION_SERVICE);
    }



    void start() {
        HandlerThread thread = new HandlerThread("BluetoothScanManager");
        thread.start();
        mHandler = new ClientHandler(thread.getLooper());
        if (mDm != null) {
            mDm.registerDisplayListener(mDisplayListener, null);
        }
        if (mActivityManager != null) {
            mActivityManager.addOnUidImportanceListener(mUidImportanceListener,
                    FOREGROUND_IMPORTANCE_CUTOFF);
        }
        IntentFilter locationIntentFilter = new IntentFilter(LocationManager.MODE_CHANGED_ACTION);
        mService.registerReceiver(mLocationReceiver, locationIntentFilter);
    }
}

常规的初始化流程，暂无特别需要介绍的内容。

3.4 PeriodicScanManager

packages/apps/Bluetooth/src/com/android/bluetooth/gatt/PeriodicScanManager.java

class PeriodicScanManager {

    static {
        classInitNative();
    }



    PeriodicScanManager(AdapterService adapterService) {
        mAdapterService = adapterService;
    }



    void start() {
        initializeNative();
    }


    private static native void classInitNative();

    private native void initializeNative();
}

packages/apps/Bluetooth/jni/com_android_bluetooth_gatt.cpp

static JNINativeMethod sPeriodicScanMethods[] = {
    {"classInitNative", "()V", (void*)periodicScanClassInitNative},
    {"initializeNative", "()V", (void*)periodicScanInitializeNative},
......
}



static void periodicScanClassInitNative(JNIEnv* env, jclass clazz) {
  method_onSyncStarted =
      env->GetMethodID(clazz, "onSyncStarted", "(IIIILjava/lang/String;III)V");
......
}



static void periodicScanInitializeNative(JNIEnv* env, jobject object) {
......
  mPeriodicScanCallbacksObj = env->NewGlobalRef(object);
}

常规的初始化流程，暂无特别需要介绍的内容。