[mounted value becomes false inside _onBackgroundFetch callback. Due to this i am unable to run setState(() {}). ]

[prema6]

Your Environment

• Plugin version: background_fetch: ^0.2.0
• Platform: Android
• OS version: Android 7.0
• Device manufacturer / model: Redmi Note 6
• Flutter info (flutter info, flutter doctor):

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.7.8+hotfix.4, on Linux, locale en_IN)

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
[✓] Android Studio (version 3.4)
[!] VS Code (version 1.34.0)
✗ Flutter extension not installed; install from
https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter
[✓] Connected device (1 available)

• Plugin config

To Reproduce
Steps to reproduce the behavior:
Calling setState((){}); throws below error when setState() called from BackgroundFetch callback

BackgroundFetch.configure(BackgroundFetchConfig(
        minimumFetchInterval: 15,
        stopOnTerminate: false,
        enableHeadless: true,
        forceReload: false
    ), () async {
      // This is the fetch-event callback.
      print('[BackgroundFetch] Event received');
      //throws error
      setState(() {
        print('@@@@@ background fetch callback - setState worked');
        _events.insert(0, new DateTime.now().toString());
      });     
      BackgroundFetch.finish();
    }).then((int status) {
      print('[BackgroundFetch] SUCCESS: $status');
      setState(() {
        _status = status;
      });
    }).catchError((e) {
      print('[BackgroundFetch] ERROR: $e');
      setState(() {
        _status = e;
      });
    });
    int status = await BackgroundFetch.status;
    setState(() {
      _status = status;
    });
    if (!mounted) return;
  }

Debug logs
D/TSBackgroundFetch( 6511): - configure: {
D/TSBackgroundFetch( 6511): "minimumFetchInterval": 15,
D/TSBackgroundFetch( 6511): "stopOnTerminate": false,
D/TSBackgroundFetch( 6511): "startOnBoot": false,
D/TSBackgroundFetch( 6511): "forceReload": false,
D/TSBackgroundFetch( 6511): "jobService": "com.transistorsoft.flutter.backgroundfetch.HeadlessJobService"
D/TSBackgroundFetch( 6511): }
D/TSBackgroundFetch( 6511): - start
I/flutter ( 6511): [BackgroundFetch] SUCCESS: 2
D/TSBackgroundFetch( 6511): - Background Fetch event received
I/flutter ( 6511): [BackgroundFetch] Event received
E/flutter ( 6511): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: setState() called after dispose(): _HomePageState#53dc8(lifecycle state: defunct, not mounted)
E/flutter ( 6511): This error happens if you call setState() on a State object for a widget that no longer appears in the widget tree (e.g., whose parent widget no longer includes the widget in its build). This error can occur when code calls setState() from a timer or an animation callback.
E/flutter ( 6511): The preferred solution is to cancel the timer or stop listening to the animation in the dispose() callback. Another solution is to check the "mounted" property of this object before calling setState() to ensure the object is still in the tree.
E/flutter ( 6511): This error might indicate a memory leak if setState() is being called because another object is retaining a reference to this State object after it has been removed from the tree. To avoid memory leaks, consider breaking the reference to this object during dispose().
E/flutter ( 6511): #0 State.setState. (package:flutter/src/widgets/framework.dart:1105:9)
E/flutter ( 6511): #1 State.setState (package:flutter/src/widgets/framework.dart:1140:6)
E/flutter ( 6511): #2 _HomePageState.initPlatformState. (package:demo_mobile/pages/homepage.dart:85:7)
E/flutter ( 6511):
E/flutter ( 6511): #3 BackgroundFetch.configure. (package:background_fetch/background_fetch.dart:169:17)
E/flutter ( 6511): #4 _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter ( 6511): #5 _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter ( 6511): #6 _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
E/flutter ( 6511): #7 _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
E/flutter ( 6511): #8 _DelayedData.perform (dart:async/stream_impl.dart:591:14)
E/flutter ( 6511): #9 _StreamImplEvents.handleNext (dart:async/stream_impl.dart:707:11)
E/flutter ( 6511): #10 _PendingEvents.schedule. (dart:async/stream_impl.dart:667:7)
E/flutter ( 6511): #11 _rootRun (dart:async/zone.dart:1120:38)
E/flutter ( 6511): #12 _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter ( 6511): #13 _CustomZone.runGuarded (dart:async/zone.dart:923:7)
E/flutter ( 6511): #14 _CustomZone.bindCallbackGuarded. (dart:async/zone.dart:963:23)
E/flutter ( 6511): #15 _rootRun (dart:async/zone.dart:1124:13)
E/flutter ( 6511): #16 _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter ( 6511): #17 _CustomZone.runGuarded (dart:async/zone.dart:923:7)
E/flutter ( 6511): #18 _CustomZone.bindCallbackGuarded. (dart:async/zone.dart:963:23)
E/flutter ( 6511): #19 _microtaskLoop (dart:async/schedule_microtask.dart:41:21)
E/flutter ( 6511): #20 _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5)
E/flutter ( 6511):

Additional context
Add any other context about the problem here.

[christocracy]

The /example in this repo calls setState in the fetch-callback.

[christocracy]

Show me more context of where you've placed BackgroundFetch.configure (ie: the entire component)

[prema6]

BackgroundFetch.configure is placed in my homepage.dart
I have the structure as follows:
main.dart -> if(token) => homePage.dart else loginPage.dart

<<<<<<main.dart>>>>>>>>>>>

import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:zoomme_mobile/pages/loginpage.dart';
import 'package:zoomme_mobile/pages/homepage.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:background_fetch/background_fetch.dart';

/// This "Headless Task" is run when app is terminated.
void backgroundFetchHeadlessTask() async {
  print('[BackgroundFetch] Headless event received.');
  print('@@@@@@ PREMA headless Fetch');
  SharedPreferences prefs = await SharedPreferences.getInstance();
  // Read fetch_events from SharedPreferences
  List<String> events = [];
  String json = prefs.getString(EVENTS_KEY);
  if (json != null) {
    events = jsonDecode(json).cast<String>();
  }
  // Add new event.
  events.insert(0, new DateTime.now().toString() + ' [Headless]');
  // Persist fetch events in SharedPreferences
  prefs.setString(EVENTS_KEY, jsonEncode(events));
  BackgroundFetch.finish();
}

void main() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  var token = prefs.getString('LastToken');
  //run app
  runApp(new MaterialApp(
    title: 'Demo',
    theme: buildTheme(),
    home: token == null ? LoginPage() : HomePage(),
    routes: <String, WidgetBuilder> {
      //set routes for using the navigator
      '/home': (BuildContext context) => new HomePage(),
      '/login': (BuildContext context) => new LoginPage(),
    },
  ));
  BackgroundFetch.registerHeadlessTask(backgroundFetchHeadlessTask);
}

====================================================================
<<<<< loginPage.dart >>>>>>>>

class LoginPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => new _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {

  final emailController = TextEditingController();
  final passwordController = TextEditingController();

  @override
  void initState() {
    super.initState();
    saveCurrentRoute("/login");
  }

  @override
  Widget build(BuildContext context) {
    
    final emailField = TextField(
      obscureText: false,
      style: style,
      controller: emailController,
      decoration: InputDecoration(
          contentPadding: EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
          hintText: "Email",
          border: OutlineInputBorder(borderRadius: BorderRadius.circular(32.0))
      ),
    );

    final passwordField = TextField(
      obscureText: true,
      style: style,
      controller: passwordController,
      decoration: InputDecoration(
          contentPadding: EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
          hintText: "Password",
          border: OutlineInputBorder(borderRadius: BorderRadius.circular(32.0))),
    );

    final loginButon = Material(
      elevation: 5.0,
      borderRadius: BorderRadius.circular(30.0),
      color: Colors.redAccent,
      child: MaterialButton(
        minWidth: MediaQuery.of(context)
            .size
            .width,
        padding: EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
        onPressed: () async {
          await loginAPI(context, emailController.text, passwordController.text).then((ConfigModel loginStatus) {
            if(loginStatus != null) {
              _isLoading = false;
              print('POST login passed');

              Navigator.of(context).pushReplacementNamed('/home');
              return loginStatus.authToken;
            } else {
              setState(() {
                _isLoading = false;
                emailController.text = '';
                passwordController.text = '';
              });
              print('POST login failled');
              return null;
            }
          });
        },
      ),
    );

    return Scaffold(
        body: SingleChildScrollView(
          child: Center(
            child: Container(
              color: Colors.white,
              child: Padding(
                padding: const EdgeInsets.all(36.0),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.center,
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: <Widget>[
                    SizedBox(height: 155.0),
                    SizedBox(height: 45.0),
                    emailField,
                    SizedBox(height: 25.0),
                    passwordField,
                    SizedBox(
                      height: 35.0,
                    ),
                    loginButon,
                    SizedBox(
                      height: 15.0,
                    ),
                  ],
                ),
              ),
            ),
          ),
        ),
    );
  }
}

============================================================================
<<< homePage.dart >>>>

const EVENTS_KEY = "fetch_events";

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() =>  _HomePageState();
}

class _HomePageState extends State<HomePage> {

  Geolocator geoLocator = Geolocator();
  var loginUserName = '';
  int _status = 0;
  List<String> _events = [];
  
  @override
  void initState() {
    super.initState();
    saveCurrentRoute("/home");
    getSharedPreference();
    initPlatformState();
  }

  getSharedPreference() async {
    SharedPreferences preferences = await SharedPreferences.getInstance();
    loginUserName = preferences.getString('LoginUserName');
    
    setState(() {

    });
  }

  // Platform messages are asynchronous, so we initialize in an async method.
  Future<void> initPlatformState() async {
    // Load persisted fetch events from SharedPreferences
    SharedPreferences prefs = await SharedPreferences.getInstance();
    String json = prefs.getString(EVENTS_KEY);
    if (json != null) {
      setState(() {
        _events = jsonDecode(json).cast<String>();
      });
    }

    // Configure BackgroundFetch.
    BackgroundFetch.configure(BackgroundFetchConfig(
        minimumFetchInterval: 15,
        stopOnTerminate: false,
        enableHeadless: true,
        forceReload: false
    ), _onBackgroundFetch).then((int status) {
      print('[BackgroundFetch] SUCCESS: $status');
      setState(() {
        _status = status;
      });
    }).catchError((e) {
      print('[BackgroundFetch] ERROR: $e');
      setState(() {
        _status = e;
      });
    });

    // Optionally query the current BackgroundFetch status.
    int status = await BackgroundFetch.status;
    setState(() {
      _status = status;
    });

    // If the widget was removed from the tree while the asynchronous platform
    // message was in flight, we want to discard the reply rather than calling
    // setState to update our non-existent appearance.
    if (!mounted) return;
  }

  void _onBackgroundFetch() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();

    print('[BackgroundFetch] Event received');

    if(true) {
	//this setState throws error. Mounted value false
	setState(() {
            print('set state PASS');
        });
    }

    BackgroundFetch.finish();
  }

  @override
  Widget build(BuildContext context) => new Scaffold(
    appBar: new AppBar(
      backgroundColor: Colors.red,
      title: new Text('Hi $loginUserName, '),
      actions: <Widget>[
        new FlatButton.icon(
        
        ),
      ],
    ),
    drawer: BasicDrawer(),
    body: new Card(
      child: new Column(
        children: <Widget>[
          ListTile(
            title: Text(''),
          ),
          ListTile(
            title: Text(''),
          )
        ],
      ),
    ),
  );
}

[christocracy]

Please learn to use Syntax Highlighting. It's very easy with 3-backticks + optional language:

[prema6]

okay. Will follow.

[christocracy]

Please make a simple test-case app that reproduces the problem and share that Github repo with me.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. You may also mark this issue as a "discussion" and I will leave this open.

[stale]

Closing this issue after a prolonged period of inactivity. Fell free to reopen this issue, if this still affecting you.