Lateinitializationerror field 'data' has not been initialized-CodePudding

I am new to flutter and I am trying to build an app which shows the current location by using Google Maps API. There is no error in this code but this error is coming after running: Exception has occurred. LateError (LateInitializationError: Field 'currentLocation' has not been initialized.)

Can someone please provide an example code of what's needed to solve for this error?

import 'package:geolocator/geolocator.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:location/location.dart';

void main() => runApp(const MyApp());

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  late GoogleMapController mapController;
  final Set<Marker> markers = {};
  // static const LatLng showLocation =
  late LatLng currentLocation;
  // late Widget googleMap;

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

  void getCurrentPosition() async {
    late Location location = Location();
    location.getLocation().then(
      (location) {
        currentLocation = location as LatLng; //as Future<APILocation>
      },
    );
  }

  void _onMapCreated(GoogleMapController controller) {
    mapController = controller;
  }

  Future<Position> _determinePosition() async {
    bool serviceEnabled;
    LocationPermission permission;

    // Test if location services are enabled.
    serviceEnabled = await Geolocator.isLocationServiceEnabled();
    if (!serviceEnabled) {
      // Location services are not enabled don't continue
      // accessing the position and request users of the
      // App to enable the location services.
      return Future.error('Location services are disabled.');
    }

    permission = await Geolocator.checkPermission();
    if (permission == LocationPermission.denied) {
      permission = await Geolocator.requestPermission();
      if (permission == LocationPermission.denied) {
        // Permissions are denied, next time you could try
        // requesting permissions again (this is also where
        // Android's shouldShowRequestPermissionRationale
        // returned true. According to Android guidelines
        // your App should show an explanatory UI now.
        return Future.error('Location permissions are denied');
      }
    }

    if (permission == LocationPermission.deniedForever) {
      // Permissions are denied forever, handle appropriately.
      return Future.error(
          'Location permissions are permanently denied, we cannot request permissions.');
    }

    // When we reach here, permissions are granted and we can
    // continue accessing the position of the device.
    return await Geolocator.getCurrentPosition();
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<Position>(
        future: _determinePosition(),
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            return const CircularProgressIndicator();
          }
          return GoogleMap(
            initialCameraPosition:
                CameraPosition(target: currentLocation, zoom: 15.0),
            markers: getmarkers(),
            mapType: MapType.normal,
            onMapCreated: (controller) {
              setState(() {
                mapController = controller;
              });
            },
          );
        });
  }

  Set<Marker> getmarkers() {
    setState(() {
      markers.add(
        Marker(
          markerId: MarkerId(currentLocation.toString()),
          position: currentLocation,
          infoWindow: const InfoWindow(
            title: 'Current Location',
            snippet: 'blabla',
          ),
          icon: BitmapDescriptor.defaultMarker,
        ),
      );
    });
    return markers;
  }
}

CodePudding user response：

Change your getCurrentPosition like

void getCurrentPosition() async {
  late Location location = Location();
  location.getLocation().then(
    (location) {
      currentLocation =
          LatLng(location.latitude ?? 0, location.longitude ?? 0); //this
    },
  );
}

There are others issue like

not using MaterialApp on root
using SetState on Build Time.
FutureBuilder on done returning CircularProgressBar
not sure what else I've changed, compare with your snippet

import 'package:geolocator/geolocator.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:location/location.dart';
import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: const MyApp()));

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  late GoogleMapController mapController;
  final Set<Marker> markers = {};
  // static const LatLng showLocation =
  //     LatLng(41.01358468198064, 28.86560382071653);
  late LatLng currentLocation;
  // late Widget googleMap;

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

  void getCurrentPosition() async {
    late Location location = Location();
    location.getLocation().then(
      (location) {
        currentLocation =
            LatLng(location.latitude ?? 0, location.longitude ?? 0);
      },
    );
  }

  void _onMapCreated(GoogleMapController controller) {
    mapController = controller;
  }

  Future<Position> _determinePosition() async {
    bool serviceEnabled;
    LocationPermission permission;

    // Test if location services are enabled.
    serviceEnabled = await Geolocator.isLocationServiceEnabled();
    if (!serviceEnabled) {
      // Location services are not enabled don't continue
      // accessing the position and request users of the
      // App to enable the location services.
      return Future.error('Location services are disabled.');
    }

    permission = await Geolocator.checkPermission();
    if (permission == LocationPermission.denied) {
      permission = await Geolocator.requestPermission();
      if (permission == LocationPermission.denied) {
        // Permissions are denied, next time you could try
        // requesting permissions again (this is also where
        // Android's shouldShowRequestPermissionRationale
        // returned true. According to Android guidelines
        // your App should show an explanatory UI now.
        return Future.error('Location permissions are denied');
      }
    }

    if (permission == LocationPermission.deniedForever) {
      // Permissions are denied forever, handle appropriately.
      return Future.error(
          'Location permissions are permanently denied, we cannot request permissions.');
    }

    // When we reach here, permissions are granted and we can
    // continue accessing the position of the device.
    return await Geolocator.getCurrentPosition();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FutureBuilder<Position>(
          future: _determinePosition(),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.waiting) {
              return const CircularProgressIndicator();
            }

            if (snapshot.hasError) return Text("Error");

            if (snapshot.hasData) {
              return GoogleMap(
                initialCameraPosition:
                    CameraPosition(target: currentLocation, zoom: 15.0),
                markers: getmarkers(),
                mapType: MapType.normal,
                onMapCreated: (controller) {
                  mapController = controller;
                },
              );
            }
            return CircularProgressIndicator();
          }),
    );
  }

  Set<Marker> getmarkers() {
    markers.add(
      Marker(
        markerId: MarkerId(currentLocation.toString()),
        position: currentLocation,
        infoWindow: const InfoWindow(
          title: 'Current Location',
          snippet: 'blabla',
        ),
        icon: BitmapDescriptor.defaultMarker,
      ),
    );

    return markers;
  }
}

CodePudding user response：

LateInitializationError occurs when you try to access a late variable before it's initialized. in your case, your code is trying to access currentLocation before it's assigned a value.

Now I don't know how your code works but could the reason be that you are showing a loading screen when you're loading in your build method?

Your code in build():

if (snapshot.connectionState == ConnectionState.done) {
  return const CircularProgressIndicator();
}

CodePudding user response：

I had modified your code try using this and compare with yours I had checked not getting error

import 'package:geolocator/geolocator.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:location/location.dart';
import 'package:flutter/material.dart';
void main() => runApp(const MaterialApp(home: MyApp()));

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState( );
}

class _MyAppState extends State<MyApp> {
  late GoogleMapController mapController;
  final Set<Marker> markers = {};
  // static const LatLng showLocation =
  //     LatLng(41.01358468198064, 28.86560382071653);
  late LatLng currentLocation;
  // late Widget googleMap;
  // _MyAppState({this.currentLocation});
  @override
  void initState() {
    super.initState();
    // getCurrentPosition();
  }

  // void getCurrentPosition() async {
  //   late Location location = Location();
  //  await location.getLocation().then(
  //         (location) {
  //       currentLocation = location; //as Future<APILocation>
  //     },
  //   );
  // }

  void _onMapCreated(GoogleMapController controller) {
    mapController = controller;
  }

  Future<Position> _determinePosition() async {
    bool serviceEnabled;
    LocationPermission permission;

    // Test if location services are enabled.
    serviceEnabled = await Geolocator.isLocationServiceEnabled();
    if (!serviceEnabled) {
      // Location services are not enabled don't continue
      // accessing the position and request users of the
      // App to enable the location services.
      return Future.error('Location services are disabled.');
    }

    permission = await Geolocator.checkPermission();
    if (permission == LocationPermission.denied) {
      permission = await Geolocator.requestPermission();
      if (permission == LocationPermission.denied) {
        // Permissions are denied, next time you could try
        // requesting permissions again (this is also where
        // Android's shouldShowRequestPermissionRationale
        // returned true. According to Android guidelines
        // your App should show an explanatory UI now.
        return Future.error('Location permissions are denied');
      }
    }

    if (permission == LocationPermission.deniedForever) {
      // Permissions are denied forever, handle appropriately.
      return Future.error(
          'Location permissions are permanently denied, we cannot request permissions.');
    }

    // When we reach here, permissions are granted and we can
    // continue accessing the position of the device.
    return await Geolocator.getCurrentPosition();
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<Position>(
        future: _determinePosition(),
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return const CircularProgressIndicator();
          }
          if (snapshot.connectionState == ConnectionState.done) {
             currentLocation= LatLng(snapshot.data!.latitude,snapshot.data!.longitude);
             print('ffr ${snapshot.data!.latitude}');
             print('ffr ${snapshot.data!.longitude}');
          }
          return GoogleMap(
            initialCameraPosition:
            CameraPosition(target: LatLng(snapshot.data!.latitude,snapshot.data!.longitude), zoom: 15.0),
            markers: getmarkers(),
            mapType: MapType.normal,
            onMapCreated: (controller) {
                mapController = controller;
            },
          );
        });
  }

  Set<Marker> getmarkers() {

      markers.add(
        Marker(
          markerId: MarkerId(currentLocation.longitude.toString()),
          position:  LatLng(currentLocation.latitude,currentLocation.longitude),
          infoWindow: const InfoWindow(
            title: 'Current Location',
            snippet: 'blabla',
          ),
          icon: BitmapDescriptor.defaultMarker,
        ),
      );
    return markers;
  }
}