[BUG]: readCharacteristic always fail

[tree1891]

Requirements

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

Have you checked this problem on the example app?

No

FlutterBluePlus Version

1.35.0

Flutter Version

3.27.2

What OS?

Android

OS Version

Android 10

Bluetooth Module

Nordic

What is your problem?

readCharacteristic always fail, but not in 1.34.5.
It seems to be called before onDescriptorWrite finish.

Logs

D/[FBP-Android](16804): [FBP] onMethodCall: flutterRestart
D/[FBP-Android](16804): [FBP] initializing BluetoothAdapter
D/[FBP-Android](16804): [FBP] disconnectAllDevices(flutterRestart)
D/[FBP-Android](16804): [FBP] connectedPeripherals: 0
D/[FBP-Android](16804): [FBP] onMethodCall: isSupported
D/[FBP-Android](16804): [FBP] onMethodCall: getAdapterState
I/flutter (16804): [FBP] stopScan: already stopped
D/[FBP-Android](16804): [FBP] onMethodCall: startScan
D/BluetoothAdapter(16804): isLeEnabled(): ON
D/BluetoothLeScanner(16804): onScannerRegistered() - status=0 scannerId=7 mScannerId=0
D/[FBP-Android](16804): [FBP] onMethodCall: stopScan
D/BluetoothAdapter(16804): isLeEnabled(): ON
D/[FBP-Android](16804): [FBP] onMethodCall: connect
D/BluetoothGatt(16804): connect() - device: D8:3B:DA:4D:B1:CA, auto: false
D/BluetoothGatt(16804): registerApp()
D/BluetoothGatt(16804): registerApp() - UUID=a46690e8-094b-4d0e-80ec-9b6af66cf9f3
D/BluetoothGatt(16804): onClientRegistered() - status=0 clientIf=7
D/BluetoothGatt(16804): onClientConnectionState() - status=0 clientIf=7 device=D8:3B:DA:4D:B1:CA
D/[FBP-Android](16804): [FBP] onConnectionStateChange:connected
D/[FBP-Android](16804): [FBP]   status: SUCCESS
D/[FBP-Android](16804): [FBP] onMethodCall: requestMtu
D/BluetoothGatt(16804): configureMTU() - device: D8:3B:DA:4D:B1:CA mtu: 512
D/BluetoothGatt(16804): onConnectionUpdated() - Device=D8:3B:DA:4D:B1:CA interval=36 latency=3 timeout=500 status=0
D/BluetoothGatt(16804): onConnectionUpdated() - Device=D8:3B:DA:4D:B1:CA interval=6 latency=0 timeout=500 status=0
D/BluetoothGatt(16804): onConfigureMTU() - Device=D8:3B:DA:4D:B1:CA mtu=256 status=0
D/[FBP-Android](16804): [FBP] onMtuChanged:
D/[FBP-Android](16804): [FBP]   mtu: 256
D/[FBP-Android](16804): [FBP]   status: GATT_SUCCESS (0)
D/[FBP-Android](16804): [FBP] onMethodCall: discoverServices
D/BluetoothGatt(16804): discoverServices() - device: D8:3B:DA:4D:B1:CA
D/BluetoothGatt(16804): onSearchComplete() = Device=D8:3B:DA:4D:B1:CA Status=0
D/[FBP-Android](16804): [FBP] onServicesDiscovered:
D/[FBP-Android](16804): [FBP]   count: 6
D/[FBP-Android](16804): [FBP]   status: 0GATT_SUCCESS
D/BluetoothGatt(16804): onConnectionUpdated() - Device=D8:3B:DA:4D:B1:CA interval=36 latency=3 timeout=500 status=0
D/[FBP-Android](16804): [FBP] onMethodCall: setNotifyValue
D/BluetoothGatt(16804): setCharacteristicNotification() - uuid: 00002a05-0000-1000-8000-00805f9b34fb enable: true
D/[FBP-Android](16804): [FBP] onMethodCall: readCharacteristic
[LinkPage] Exception in connectDevice
D/[FBP-Android](16804): [FBP] onMethodCall: disconnect
D/BluetoothGatt(16804): cancelOpen() - device: D8:3B:DA:4D:B1:CA
D/BluetoothGatt(16804): onClientConnectionState() - status=0 clientIf=7 device=D8:3B:DA:4D:B1:CA
D/[FBP-Android](16804): [FBP] onConnectionStateChange:disconnected
D/[FBP-Android](16804): [FBP]   status: SUCCESS
D/BluetoothGatt(16804): close()
D/BluetoothGatt(16804): unregisterApp() - mClientIf=7
           PlatformException(readCharacteristic, gatt.readCharacteristic() returned false, null, null)
           #0      StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:646:7)
           #1      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:334:18)
           <asynchronous suspension>
           #2      FlutterBluePlusAndroid._invokeMethod (package:flutter_blue_plus_android/flutter_blue_plus_android.dart:400:20)
           <asynchronous suspension>
           #3      FlutterBluePlusAndroid.readCharacteristic (package:flutter_blue_plus_android/flutter_blue_plus_android.dart:232:5)
           <asynchronous suspension>
           #4      FlutterBluePlus._invokeMethod (package:flutter_blue_plus/src/flutter_blue_plus.dart:568:14)
           <asynchronous suspension>
           #5      BluetoothCharacteristic.read (package:flutter_blue_plus/src/bluetooth_characteristic.dart:124:7)
           <asynchronous suspension>
           #6      _LinkPageState.connectDevice (package:geolink/pages/link.dart:904:15)
           <asynchronous suspension>

[tnc1997]

Hi @tree1891, thanks for raising this issue, looking at the logs it appears that the Bluetooth device is disconnected.

[tree1891]

No, it is disconnected after exception occurs. It is by design.
if try to read some later after discover services, it success

D/[FBP-Android](16804): [FBP] onMethodCall: readCharacteristic
[LinkPage] Exception in connectDevice
D/[FBP-Android](16804): [FBP] onMethodCall: disconnect

[tnc1997]

No, it is disconnected after exception occurs.

Ah, I see, the logs are not ordered in chronological order, so I was reading the stack trace after the disconnection.

[tree1891]

    // in order to match iOS behavior on all platforms,
    // we always listen to the Services Changed characteristic if it exists.

It seems that readCharacteristic is called before onDescriptorWrite finish for setNotifyValue.

[tnc1997]

Does the same exception get thrown if subscribeToServicesChanged is false when calling discoverServices?

[tree1891]

no problem if subscribeToServicesChanged is false

[tnc1997]

Thank you very much for confirming that, it sounds like there may be a synchronisation issue.

[tnc1997]

This issue may be related to #1102 whereby the previous operation has not completed before the next one starts.

[tnc1997]

@tree1891 would I be able to get you to confirm if you still experience this issue with the fix/1102 branch?

dependency_overrides:
  flutter_blue_plus_android:
    git:
      url: https://github.com/chipweinberger/flutter_blue_plus.git
      ref: fix/1102
      path: packages/flutter_blue_plus_android

[tree1891]

It does work well.

[tnc1997]

It does work well.

Thank you for confirming that change fixes this issue, we will publish some patched versions to pub.dev.

[chipweinberger]

update to 1.35.1