flutterBlue.connect(device, timeout: const Duration(seconds: 10),).listen(null); in flutter - flutter

Question

sorry,I am a beginner and my English is very bad
i have a trouble in Flutter.
i reference https://pub.dartlang.org/packages/flutter_blue
I want to use flutter to communicate with the ear thermometer device.
when i reopen bluetooth and it can work,but I reopen app and excute second it show error.
i guess bluetooth gatt cahce is causing a error.
how can i solve it?
my code
deviceConnection = flutterBlue.scan(timeout: const Duration(seconds: 5),).listen((scanResult) async {
device = scanResult.device;
deviceConnection2 = await flutterBlue.connect(device, timeout: const Duration(seconds: 10),).listen(null);//this line error is error 1
deviceStateSubscription = device.onStateChanged().listen((s) async {
await device.discoverServices().then((s) async {//this is error 2
.........
}
}
}
it show these error
error 1
Dart Error: Unhandled exception:
PlatformException(already_connected, connection with device already exists, null)
error 2
Dart Error: Unhandled exception:
PlatformException(get_services_error, no instance of BluetoothGatt, have you connected first?, null)

Answer 1

Error 1
Dart Error: Unhandled exception: PlatformException(already_connected, connection with device already exists, null)
Since the app detected that a bluetooth device is already connected, one workaround is check for any connected device disconnect it. You can create a function that does this like the one in this GitHub thread:
What you can do here is that you check for any connected devices and
then disconnect them. I have written a function that does just that,
here it is:
checkConnectedDevices() async{
connectedDevices = await flutterBlue.connectedDevices.whenComplete((){
print(connectedDevices);
for(int i = 0; i < connectedDevices.length; i++){
connectedDevices[i].disconnect();
}
});
}
Error 2
Dart Error: Unhandled exception: PlatformException(get_services_error, no instance of BluetoothGatt, have you connected first?, null)
Since there is an error connecting to the device, you will not be able to call the discoverServices(). Because you need to be connected to a device before you can call this function. Check the following GitHub discussions related to this error:
connected ' discoverServices ' is't get #426
discoverServices is broken #535