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Question

I’m building a Flutter app which will use EventChannel and MethodChannel that will communicate between Native and Flutter code. I’m using the IOS Region Monitoring to detect if the user have exited or entered the region.

On the Flutter side, I will check for all necessary permissions before passing the regions to the Native side through Method Channel for region monitoring and uses EventChannel to inform the Flutter side that the user have either exited or entered the region. Everything works as expected when the app is in alive in foreground or in the background. However, when I terminate the app, the region monitoring doesn’t seem to work anymore.

I tried this prototype which is fully native, it works perfectly on foreground, background and terminated state.

Below is my code on the Native side

import UIKit
import CoreLocation
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  var locationManager: CLLocationManager!
  var eventSink: FlutterEventSink?
  var regions: [CLCircularRegion] = []
    
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    let controller = window?.rootViewController as! FlutterViewController
    let channel = FlutterMethodChannel(name: "location", binaryMessenger: controller.binaryMessenger)
    let eventChannel = FlutterEventChannel(name: "location_stream", binaryMessenger: controller.binaryMessenger)
    channel.setMethodCallHandler(handle)
    eventChannel.setStreamHandler(self)

    locationManager = CLLocationManager()
    locationManager.delegate = self
      
    GeneratedPluginRegistrant.register(with: self)
      
    if launchOptions?[UIApplication.LaunchOptionsKey.location] != nil  {
        NSLog("regrion monitoring: launchoptionkey")
        if locationManager == nil {
            locationManager = CLLocationManager()
            locationManager.delegate = self
            startMonitoring()
        }
        eventSink?(["type": 2, "identifier": "woke up"])
    }
      
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
    
  public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
    print("regrion monitoring: here")
    switch call.method {
    case "startMonitoring":
        startMonitoring()
        result(nil)
    case "stopMonitoring":
        stopMonitoring()
        result(nil)
    case "setRegions":
        setRegions(call: call)
        result(nil)
    default:
        result(FlutterMethodNotImplemented)
    }
  }
    
  private func startMonitoring() {
    print("regrion monitoring: start")
      eventSink?(["type": 3, "identifier": "startMonitoring"])
    for o in regions {
        eventSink?(["type": 3, "identifier": "startMonitoring: (o.identifier)"])
        print("regrion monitoring: (o.identifier)")
        o.notifyOnExit = true;
        o.notifyOnEntry = true;
        locationManager.startMonitoring(for: o)
    }
  }
    
  private func stopMonitoring() {
    print("regrion monitoring: stop")
    for o in regions {
        locationManager.stopMonitoring(for: o)
    }
//    locationManager.delegate = nil
    eventSink = nil
  }
    
  private func setRegions(call: FlutterMethodCall) {
    let argResult = call.arguments as? [String: [String: Any]]
    for s in argResult!.keys {
        print("regrion monitoring: (s)");
        regions.append(CLCircularRegion(
            center: CLLocationCoordinate2D(latitude: argResult![s]!["latitude"] as! Double, longitude: argResult![s]!["longitude"] as! Double),
            radius: argResult![s]!["radius"] as! Double,
            identifier: argResult![s]!["description"] as! String))
    }
  }
    
  private func handleEvent(forRegion region: CLRegion, type: Int) {
    print("regrion monitoring: (region.identifier)")
        
    eventSink?(["type": type, "identifier": region.identifier])
    print("regrion monitoring: after event sink")
  }
}

extension AppDelegate: CLLocationManagerDelegate {
    public func locationManager(_ manager: CLLocationManager, didStartMonitoringFor region: CLRegion) {
        print("regrion monitoring: didStartMonitoring")
        print("(region.identifier)")
    }
    
    public func locationManager(_ manager: CLLocationManager, didEnterRegion region: CLRegion) {
        print("regrion monitoring: Enter")
        if region is CLCircularRegion {
            handleEvent(forRegion: region, type: 0)
        }
    }
    
    public func locationManager(_ manager: CLLocationManager, didExitRegion region: CLRegion) {
        print("regrion monitoring: Exit")
        if region is CLCircularRegion {
            handleEvent(forRegion: region, type: 1)
        }
    }
}

extension AppDelegate: FlutterStreamHandler {
    @objc public func onListen(withArguments arguments: Any?, eventSink events: @escaping FlutterEventSink) -> FlutterError? {
        print("onListen")
        self.eventSink = events
        return nil
    }
    
    @objc public func onCancel(withArguments arguments: Any?) -> FlutterError? {
        print("onCancel")
        self.eventSink = nil
        return nil
    }
}

Flutter code as below:
main.dart

import 'package:flutter/material.dart';
import 'package:regrion_monitoring/location.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();

  runApp(const MainApp());
}

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

  @override
  State<MainApp> createState() => _MainAppState();
}

class _MainAppState extends State<MainApp> {
  @override
  void initState() {
    super.initState();
    requestLocationService().then((value) async {
      if (value) {
        await requestLocationPermission();
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            appBar: AppBar(title: const Text('Region Monitoring')),
            body: Center(
                child: Column(children: [
              FilledButton(
                  onPressed: () async => await LocationHelper().setRegions(),
                  child: const Text('Set Region')),
              FilledButton(
                  onPressed: () async => await LocationHelper().start(),
                  child: const Text('Start Monitor')),
              FilledButton(
                  onPressed: () async => await LocationHelper().stop(),
                  child: const Text('Stop Monitor'))
            ]))));
  }
}

location.dart

import 'dart:async';
import 'dart:io';
import 'package:flutter/services.dart';
import 'package:geolocator/geolocator.dart';
import 'package:location/location.dart' as location;
import 'package:permission_handler/permission_handler.dart' as permission;

class LocationHelper {
  static final LocationHelper _instance = LocationHelper._internal();

  LocationHelper._internal();

  factory LocationHelper() => _instance;

  final MethodChannel channel = const MethodChannel('location');

  final EventChannel eventChannel = const EventChannel('location_stream');

  Future<void> start() async {
    print('regrion monitoring: start');
    await channel.invokeMethod('startMonitoring');
    eventChannel.receiveBroadcastStream().listen((event) {
      Map<String, dynamic> result = Map<String, dynamic>.from(event as Map);
      print('receiveBroadcastStream');
      print('regrion monitoring: identifier: ${result['identifier']}');
      print('regrion monitoring: type: ${result['type']}');
    });
  }

  Future<void> stop() async {
    print('regrion monitoring: stop');
    await channel.invokeMethod('stopMonitoring');
  }

  Future<void> setRegions() async {
    Map<String, dynamic> regions = {
      'location1': {
        'latitude': 3.1067979,
        'longitude': 101.4466574,
        'radius': 60,
        'description': 'Lotus'
      },
      'location2': {
        'latitude': 3.1072308,
        'longitude': 101.4387836,
        'radius': 60,
        'description': 'NSK'
      };
    print('regrion monitoring: setRegions');
    await channel.invokeMethod('setRegions', regions);
  }
}

Future<bool> requestLocationService() async {
  if (!await Geolocator.isLocationServiceEnabled()) {
    if (Platform.isAndroid) {
      await location.Location().requestService();
      if (!await location.Location().serviceEnabled()) {
        return false;
      }
    } else if (Platform.isIOS || Platform.isMacOS) {
      await Geolocator.openLocationSettings();
    }
  }
  return true;
}

Future<bool> requestLocationPermission() async {
  if (await permission.Permission.locationWhenInUse.isDenied) {
    await permission.Permission.locationWhenInUse.request();
  }

  if (await permission.Permission.locationWhenInUse.isGranted &&
      !await permission.Permission.locationAlways.isGranted) {
    if (Platform.isIOS || Platform.isMacOS) {
      await permission.Permission.locationAlways.request();
    }
    if (await permission.Permission.locationAlways.isDenied) {
      return false;
    }
  }

  // if location permission is permanently denied
  if (await permission.Permission.locationWhenInUse.isPermanentlyDenied) {
    await permission.openAppSettings();
  }

  return true;
}

I have also set these two properties (Location Always and When In Use and Location Always and When In Use) in info.plist

I have also tried calling startMonitoring in applicationWillTerminate but it still doesn’t work. Can anyone help me?

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Danh mục

IOS Region Monitoring not working when app is terminated (Flutter)