Event listeners stops working after another plugin initialization

[estevez-dev]

System info

Issue occurs on: Android
Plugin version: 0.3.7
Flutter doctor output:

[✓] Flutter (Channel stable, v1.7.8+hotfix.4, on Linux, locale en_US.UTF-8)
 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
[✓] Android Studio (version 3.5)
[!] Connected device
    ! No devices available

! Doctor found issues in 1 category.

Steps to Reproduce

1. Use webview plugin with onUrlChanged listener attached
2. Add android_alarm_manager or workmanager plugin to your project
3. Initialize android_alarm_manager or workmanager and create an alrarm or task.

main.dart example:

...
import 'package:flutter_webview_plugin/flutter_webview_plugin.dart';
import 'package:workmanager/workmanager.dart' as workManager;

...
void callbackDispatcher() {
  workManager.Workmanager.executeTask((backgroundTask) {
    print("Native called background task: $backgroundTask"); //simpleTask will be emitted here.
    return Future.value(true);
  });
}

void main() async {
  FlutterError.onError = (errorDetails) {
    Logger.e( "${errorDetails.exception}");
    if (Logger.isInDebugMode) {
      FlutterError.dumpErrorToConsole(errorDetails);
    }
  };

  runZoned(() {
    workManager.Workmanager.initialize(
        callbackDispatcher,
        isInDebugMode: true
    ); 
    workManager.Workmanager.registerPeriodicTask("1", "simpleTask", frequency: Duration(hours: 1)); //Comment this line to make webview events work
    runApp(new HAClientApp());

  }, onError: (error, stack) {
    Logger.e("$error");
    Logger.e("$stack");
    if (Logger.isInDebugMode) {
      debugPrint("$stack");
    }
  });
}

class HAClientApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: "Application",
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      initialRoute: "/",
      routes: {
        "/": (context) => MainPage(title: 'HA Client'),
        "/login": (context) => WebviewScaffold(
          url: "${ConnectionManager().oauthUrl}",
          appBar: new AppBar(
            title: new Text("Login"),
          ),
        ),
      },
    );
  }
}
...

Webview calling somewhere in code:

final flutterWebviewPlugin = new FlutterWebviewPlugin();
flutterWebviewPlugin.onUrlChanged.listen((String url) {
    print("Url changed to: $url");
});
Navigator.of(context).pushNamed('/login');

Comment workManager.Workmanager.registerPeriodicTask and webview onUrlChanged will start working. Also need to mention that android_alarm_manager and workmanager register itself in java application class. For example:

package com.keyboardcrumbs.hassclient;

import io.flutter.app.FlutterApplication;
import io.flutter.plugin.common.PluginRegistry;
import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback;
import io.flutter.plugins.GeneratedPluginRegistrant;
import be.tramckrijte.workmanager.WorkmanagerPlugin;

public class Application extends FlutterApplication implements PluginRegistrantCallback {
    @Override
    public void onCreate() {
        super.onCreate();
        WorkmanagerPlugin.setPluginRegistrantCallback(this);
    }

    @Override
    public void registerWith(PluginRegistry registry) {
        GeneratedPluginRegistrant.registerWith(registry);
    }
}

Logs

No errors in log

$ flutter doctor -v
[✓] Flutter (Channel stable, v1.7.8+hotfix.4, on Linux, locale en_US.UTF-8)
    • Flutter version 1.7.8+hotfix.4 at /home/estevez/sdk/flutter
    • Framework revision 20e59316b8 (8 weeks ago), 2019-07-18 20:04:33 -0700
    • Engine revision fee001c93f
    • Dart version 2.4.0

 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at /home/estevez/Android/Sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-29, build-tools 29.0.2
    • Java binary at: /home/estevez/bin/android-studio/jre/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
    • All Android licenses accepted.

[✓] Android Studio (version 3.5)
    • Android Studio at /home/estevez/bin/android-studio
    • Flutter plugin version 39.0.3
    • Dart plugin version 191.8423
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)

[!] Connected device
    ! No devices available

! Doctor found issues in 1 category.

[charafau]

Thanks for the issue, I was also reading discussion from other plugin. Is it only that one plugin or for whole alarm manager ?

[estevez-dev]

I reproduced this issue only with those two plugins. The only difference is that for workmanager you need to call registerPeriodicTask and for alarm manager you just need to initialize it.

[estevez-dev]

Hi @charafau , there is some additional info available from workmanager plugin developer: fluttercommunity/flutter_workmanager#64 (comment)

[charafau]

thanks for investigation, not sure how to fix it yet, needs more fixing

[timrijckaert]

If we do not re-register your plugins inside the background Isolate then the stream in your main Isolate will still receive update from the flutter_webview.

However, as a user you want to be able to use your plugins also in the background.

[estevez-dev]

@charafau may be it is possible to re-create event streams? For example with some publicly available method that will close the streams and create a new one? I now, I need to reattach listeners to the streams then, but this is not a problem. If it is possible lets test it in separate branch, I'm ready for testing ;-)

[charafau]

@estevez-dev probably yes.. but my time is very limited and I barely manage to do reviews and commits to project currently. If you create PR with fixes, that would be really helpful

[estevez-dev]

@charafau I totally understand you! Will try to find some time to look at the code.

[Abarth91]

Any News?

[estevez-dev]

No. I was forced to stop using webview plugin because of this issue. Moved to Chrome custom tabs.

[estevez-dev]

Still would be good this to be fixed.

[oliverbytes]

I can confirm this plugin https://pub.dev/packages/flutter_downloader also conflicts with this... listeners are not fired