Android BLE API：未收到GATT回调

Question

I working on an app that connects to a BLE device on a bike. The app works fine on Android 4.x but on Android 5 we don't get any callback on the writeCharacterstic() call. Any help is very appreciated since we are stuck at the moment!

All calls to the gatt seems to return true. I have made sure that the calls are in the correct order so the GATT server won't return status busy:

device.connectGatt()
onConnectionStateChange() -> gatt.discoverServices()
onServicesDiscovered() -> gatt.writeDescriptor()
onDescriptorWrite() -> sendRequest()
sendRequest() -> gatt.writeCharacteristic()

I've been testing on the following devices:

• Samsung Galaxy S4 with Android 4.4.2 (working)
• Samsung Galaxy S3 with Android 4.3 (working)
• LG Nexus 4 with Android 5.0.1 ( not working, no callback on writeCharacteristic() )

Code:

private BluetoothGattCallback callback = new BluetoothGattCallback() {
    @Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
        super.onConnectionStateChange(gatt, status, newState);

        if (newState == BluetoothGatt.STATE_CONNECTED) {
            Log.i(TAG, "onConnectionStateChange() - STATE_CONNECTED");
            boolean discoverServicesOk = gatt.discoverServices();
        } else if (newState == BluetoothGatt.STATE_DISCONNECTED) {
            Log.i(TAG, "onConnectionStateChange() - STATE_DISCONNECTED");
        }
    }

    @Override
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
        super.onServicesDiscovered(gatt, status);
        Log.i(TAG, "onServicesDiscovered()");

        BluetoothGattService service = gatt.getService(UART_UUID);
        characteristic = service.getCharacteristic(TX_UUID);

        boolean result = gatt.setCharacteristicNotification(characteristic, true);
        Log.i(TAG, "onServicesDiscovered() - setCharacteristicNotification " + result);

        if (characteristic.getDescriptor(CLIENT_UUID) != null) {
            BluetoothGattDescriptor desc = characteristic.getDescriptor(CLIENT_UUID);
            result = desc.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
            Log.i(TAG, "onServicesDiscovered() - ENABLE_NOTIFICATION_VALUE " + result);
            result = desc.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
            Log.i(TAG, "onServicesDiscovered() - ENABLE_INDICATION_VALUE " + result);
            result = gatt.writeDescriptor(desc);
            Log.i(TAG, "onServicesDiscovered() - writeDescriptor " + result);
        }

        connectionState = STATE_CONNECTED;
    }

    @Override
    public void onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status) {
        super.onDescriptorWrite(gatt, descriptor, status);
        mCurrentRequest = getNextRequest();
        Log.i(TAG, "onDescriptorWrite() - sending request, type: " + mCurrentRequest.getType());
        sendRequest(mCurrentRequest);
    }

    @Override
    public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
        super.onCharacteristicChanged(gatt, characteristic);

        // DON'T GET HERE ON LOLLIPOP
        Log.d(TAG, "onCharacteristicChanged() - size: " + characteristic.getValue().length + ", type: " + mCurrentRequest.getType());
    }
}

public void sendRequest(AsciiRequest asciiRequest) {
    start = System.currentTimeMillis();
    if (characteristic != null && connectionState == STATE_CONNECTED) {
        Log.i(TAG, "sendRequest() - sending request, type: " + mCurrentRequest.getType());
        characteristic.setValue(asciiRequest.getData());
        characteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);
        boolean result = gatt.writeCharacteristic(characteristic);
        Log.i(TAG, "sendRequest() - result writeCharacteristic: " + result);
    } else {
        Log.e(TAG, "sendRequest() - not connected");
    }
}

Logs:

03-31 14:08:28.614: I/BikeActivity(30045): onResume() - not connected yet, trying to connect
03-31 14:08:28.616: I/BikeActivity(30045): doConnect() - connecting to device Bike 2
03-31 14:08:28.634: I/BikeActivity(30045): doConnect() - connected to device Bike 2
03-31 14:08:29.137: I/BikeActivity(30045): onConnectionStateChange() - STATE_CONNECTED
03-31 14:08:29.151: I/BikeActivity(30045): onConnectionStateChange() - connected to device Bike 2
03-31 14:08:29.164: I/BikeActivity(30045): onServicesDiscovered()
03-31 14:08:29.170: I/BikeActivity(30045): onServicesDiscovered() - setCharacteristicNotification true
03-31 14:08:29.170: I/BikeActivity(30045): onServicesDiscovered() - ENABLE_NOTIFICATION_VALUE true
03-31 14:08:29.170: I/BikeActivity(30045): onServicesDiscovered() - ENABLE_INDICATION_VALUE true
03-31 14:08:29.172: I/BikeActivity(30045): onServicesDiscovered() - writeDescriptor true
03-31 14:08:29.173: I/BikeActivity(30045): onDescriptorWrite() - sending request, type: 25
03-31 14:08:29.182: I/BikeActivity(30045): sendRequest() - sending request, type: 25
03-31 14:08:29.186: I/BikeActivity(30045): sendRequest() - result writeCharacteristic: true
03-31 14:08:34.182: I/BikeActivity(30045): doDisconnect() - disconnecting from device Bike 2
03-31 14:08:34.233: I/BikeActivity(30045): onConnectionStateChange() - STATE_DISCONNECTED
03-31 14:08:34.233: I/BikeActivity(30045): onConnectionStateChange() - disconnected
03-31 14:08:34.263: I/BikeActivity(30045): doDisconnect() - toastText: No response from bike.
03-31 14:08:34.318: I/BikeActivity(30045): onPause()
03-31 14:08:34.712: I/BikeActivity(30045): onDestroy()

Answer 1

I understand that it is late answer, but maybe it will help somebody other with such situation. I have the same bug with Android 5 devices - note that you have disconnection event instead of writing characterictic. Try to add empty callback:

public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) 
    {
    }

it helped me with Android 5 devices.