cancelDiscovery() automatically called by flutter_bluetooth_serial library

[MukalDadhwal]

I want to connect my device with other devices from the app. I implemented almost the same the code from the documentation but after calling startDiscovery() function in the app's init state cancelDiscovery is instantly called by the app for no reason. The code successfully ran for first two or three times but starts producing the following error afterwards

D/BluetoothAdapter(15019): startDiscovery(): called by: com.example.bluetooth_app
D/FlutterBluePlugin(15019): Canceling discovery (stream closed)
D/BluetoothAdapter(15019): cancelDiscovery(): called by: com.example.bluetooth_app

Not sure what is going on. I am using flutter 3.7 and package version 0.4.0[latest]

Here's the code for the complete app -

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_bluetooth_serial/flutter_bluetooth_serial.dart';

class FooPage extends StatefulWidget {
  const FooPage({super.key});

  @override
  State<FooPage> createState() => _FooPageState();
}

class _FooPageState extends State<FooPage> {
  List<BluetoothDiscoveryResult> devices = [];

  late StreamSubscription<BluetoothDiscoveryResult>
      _discoveryStreamSubscription;

  @override
  void initState() {
    super.initState();
    _startDiscovery();
  }

  void _startDiscovery() {
    _discoveryStreamSubscription =
        FlutterBluetoothSerial.instance.startDiscovery().listen(
      (r) {
        print('device found');
        bool deviceFound = false;
        devices.forEach((element) {
          if (element.device.address == r.device.address) {
            deviceFound = true;
          }
        });
        if (!deviceFound) {
          setState(() {
            devices.add(r);
          });
        }
      },
    );

    _discoveryStreamSubscription.onDone(() {
      setState(() {
        print('stream closed');
        // _isDiscovering = false;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    print(devices);
    return Scaffold(
      appBar: AppBar(
        title: Text("Bluetooth Devices"),
      ),
      body: devices.length == 0
          ? Center(
              child: Text('No Nearby devices can be found currently...'),
            )
          : ListView(
              children: devices
                  .map(
                    (e) => ListTile(
                      title: Text(e.device.name!),
                      subtitle: Text(e.device.type.stringValue),
                    ),
                  )
                  .toList(),
            ),
    );
  }
}

And just to mention I have all the permissions in manifest as well

    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.BLUETOOTH_SCAN" />
    <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />

Any help would be really appreciated as I am trying to solve this issue from past 3-4 days.

[ahmadfatihin]

have you got the solution for this problem?

[AviKenz]

I think the explanation can be found here:

flutter_bluetooth_serial/lib/FlutterBluetoothSerial.dart

Line 215 in a76b5f2

// `cancelDiscovery` happens automaticly by platform code when closing event sink

my understanding is, the platform cancel the scan after some period and flutter_bluetoth_serial simply follows it and also cancel/close the stream.