[Help]: During initState activation of notification for characteristic fails

[Romcik077]

Requirements

• I've looked at the README 'Common Problems' section

Have you checked this problem on the example app?

Yes

FlutterBluePlus Version

1.20.7

Flutter Version

3.13.9

What OS?

Android

OS Version

Android 11/13

Bluetooth Module

bgm210pa22jia2

What is your problem?

I have 4 services with different uuids which have. Each service have 2 characteristics the uuid for these are same form service to service:

It was done to create in flutter one widget and create for each service a instance of widget.
The State characteristic I want to use as feedback with notification from BLE device.
The problem is that is I try to call setNotifyValue for State I receive next Exception:
Exception has occurred. PlatformException (PlatformException(setNotifyValue, gatt.writeDescriptor() returned 201 : ERROR_GATT_WRITE_REQUEST_BUSY, null, null))
I tried in may different ways to do it in initState, but every time has same Exception.
If I move setNotifyValue to button somewhere in widget everything works without problem.

Logs

Log with Exception:
D/[FBP-Android](31575): [FBP] onMethodCall: getAdapterState
D/BluetoothGatt(31575): onClientRegistered() - status=0 clientIf=9
D/BluetoothGatt(31575): onClientConnectionState() - status=0 clientIf=9 device=28:76:81:44:4E:0D
D/[FBP-Android](31575): [FBP] onConnectionStateChange: status: 0 (SUCCESS) newState: connected
D/BluetoothGatt(31575): onClientConnectionState() - status=0 clientIf=9 device=28:76:81:44:4E:0D
D/[FBP-Android](31575): [FBP] onConnectionStateChange: status: 0 (SUCCESS) newState: connected
D/[FBP-Android](31575): [FBP] onMethodCall: discoverServices
D/BluetoothGatt(31575): discoverServices() - device: 28:76:81:44:4E:0D
D/[FBP-Android](31575): [FBP] onMethodCall: getAdapterState
D/BluetoothGatt(31575): onConnectionUpdated() - Device=28:76:81:44:4E:0D interval=6 latency=0 timeout=500 status=0
D/BluetoothGatt(31575): onSearchComplete() = Device=28:76:81:44:4E:0D Status=0
D/[FBP-Android](31575): [FBP] onServicesDiscovered: count: 9 status: 0
D/[FBP-Android](31575): [FBP] onMethodCall: discoverServices
D/BluetoothGatt(31575): discoverServices() - device: 28:76:81:44:4E:0D
D/BluetoothGatt(31575): onSearchComplete() = Device=28:76:81:44:4E:0D Status=0
D/[FBP-Android](31575): [FBP] onServicesDiscovered: count: 9 status: 0
D/BluetoothGatt(31575): onConnectionUpdated() - Device=28:76:81:44:4E:0D interval=36 latency=0 timeout=500 status=0
D/[FBP-Android](31575): [FBP] onMethodCall: readCharacteristic
2
D/[FBP-Android](31575): [FBP] onMethodCall: getAdapterState
D/[FBP-Android](31575): [FBP] onCharacteristicRead: uuid: 00003010-0000-1000-8000-00805f9b34fb status: 0
D/[FBP-Android](31575): [FBP] onMethodCall: readCharacteristic
D/[FBP-Android](31575): [FBP] onMethodCall: setNotifyValue
D/BluetoothGatt(31575): setCharacteristicNotification() - uuid: 00003011-0000-1000-8000-00805f9b34fb enable: true
D/[FBP-Android](31575): [FBP] onCharacteristicRead: uuid: 00003010-0000-1000-8000-00805f9b34fb status: 0

Logs with setNotifyValue commented in initState:
D/BluetoothGatt(31575): discoverServices() - device: 28:76:81:44:4E:0D
D/[FBP-Android](31575): [FBP] onMethodCall: getAdapterState
D/BluetoothGatt(31575): onConnectionUpdated() - Device=28:76:81:44:4E:0D interval=6 latency=0 timeout=500 status=0
D/BluetoothGatt(31575): onSearchComplete() = Device=28:76:81:44:4E:0D Status=0
D/[FBP-Android](31575): [FBP] onServicesDiscovered: count: 9 status: 0
D/[FBP-Android](31575): [FBP] onMethodCall: readRssi
D/BluetoothGatt(31575): readRssi() - device: 28:76:81:44:4E:0D
D/[FBP-Android](31575): [FBP] onReadRemoteRssi: rssi: -52 status: 0
D/[FBP-Android](31575): [FBP] onMethodCall: getAdapterState
D/BluetoothGatt(31575): onConnectionUpdated() - Device=28:76:81:44:4E:0D interval=36 latency=0 timeout=500 status=0
D/[FBP-Android](31575): [FBP] onMethodCall: readCharacteristic
D/[FBP-Android](31575): [FBP] onMethodCall: getAdapterState
D/[FBP-Android](31575): [FBP] onCharacteristicRead: uuid: 00003010-0000-1000-8000-00805f9b34fb status: 0
D/[FBP-Android](31575): [FBP] onMethodCall: readCharacteristic
D/[FBP-Android](31575): [FBP] onMethodCall: getAdapterState
D/[FBP-Android](31575): [FBP] onCharacteristicRead: uuid: 00003010-0000-1000-8000-00805f9b34fb status: 0
D/[FBP-Android](31575): [FBP] onMethodCall: readCharacteristic
D/[FBP-Android](31575): [FBP] onMethodCall: getAdapterState
D/[FBP-Android](31575): [FBP] onCharacteristicRead: uuid: 00003010-0000-1000-8000-00805f9b34fb status: 0
D/[FBP-Android](31575): [FBP] onMethodCall: readCharacteristic
D/[FBP-Android](31575): [FBP] onMethodCall: getAdapterState
D/[FBP-Android](31575): [FBP] onCharacteristicRead: uuid: 00003010-0000-1000-8000-00805f9b34fb status: 0
D/[FBP-Android](31575): [FBP] onMethodCall: stopScan
D/BluetoothAdapter(31575): isLeEnabled(): ON

[Romcik077]

Important thing: If I try to process only one service instead of 4 or 2, the setNotifyValue call in initState works without problems.

[chipweinberger]

you should always use await when calling any FBP function.

you should not be calling setNotifyValue or any other FBP call in initState.

[Romcik077]

I add await.
This is my code from initState, in different ways:

   _controlCharacteristic.read().then((value) async {
      for (int i = 0; i < _selectedFunctionality.length; i++) {
        _selectedFunctionality[i] = i == value[0];
      }
    });
    WidgetsBinding.instance.addPostFrameCallback((timeStamp) async {
      await _stateCharacteristic.setNotifyValue(_stateCharacteristic.isNotifying == false);
    });

Every time same result.

[Romcik077]

you should not be calling setNotifyValue or any other FBP call in initState.

OK, but how I can automatically activate notification for characteristic. Should I create a delay?

[chipweinberger]

try 1.21.0

i've made the await internal to the FBP library so that users do not need to worry about it.

btw, you should always be checking for errors either with try/catch or catchError because setNotifyValue can fail!

[Romcik077]

Hello!
Now it works!
Thanks! Issue can be closed.