LateInitializationError: Field 'initialPosition' has not been initialized - flutter

Question

I am trying to create map screen but I found the below error:
======== Exception caught by widgets library =======================================================
The following LateError was thrown building Consumer<MapViewModel>(dirty, dependencies: [_InheritedProviderScope<MapViewModel>]):
LateInitializationError: Field 'initialPosition' has not been initialized.
The relevant error-causing widget was:
Consumer<MapViewModel> file:///Users/mahmoudalharoon/Desktop/Air%20Forces/aireforces/lib/screens/BaseScreen.dart:44:14
When the exception was thrown, this was the stack:
#0 MapViewModel.initialPosition (package:airforces/screens/map/viewmodel/map_viewmodel.dart)
#1 MapScreen.build.<anonymous closure> (package:airforces/screens/map/view/map_screen.dart:19:27)
#2 Consumer.buildWithChild (package:provider/src/consumer.dart:180:19)
#3 SingleChildStatelessWidget.build (package:nested/nested.dart:259:41)
#4 StatelessElement.build (package:flutter/src/widgets/framework.dart:4648:28)
...
====================================================================================================
and this is the below ViewModel I have:
import 'package:airforces/enums/ScreenState.dart';
import 'package:airforces/screens/BaseViewModel.dart';
import 'package:geocoding/geocoding.dart';
import 'package:geolocator/geolocator.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
class MapViewModel extends BaseViewModel {
late LatLng? initialPosition;
late LatLng lastMapPosition = initialPosition!;
void getUserLocation() async {
Position position = await Geolocator.getCurrentPosition(
desiredAccuracy: LocationAccuracy.high);
List<Placemark> placemarks = await placemarkFromCoordinates(
position.latitude, position.longitude);
initialPosition = LatLng(position.latitude, position.longitude);
print('${placemarks[0].name}');
setState(ViewState.Idle);
}
}
and this is the below map screen I have:
import 'package:airforces/screens/BaseScreen.dart';
import 'package:airforces/screens/map/viewmodel/map_viewmodel.dart';
import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
class MapScreen extends StatelessWidget {
#override
Widget build(BuildContext context) {
return BaseScreen<MapViewModel>(
onFinish: (_) {
},
onModelReady: (mapViewModel) {
mapViewModel.getUserLocation();
},
builder: (context, mapViewModel, child){
return GoogleMap(
initialCameraPosition: CameraPosition(
target: mapViewModel.initialPosition!,
),
myLocationEnabled: true,
);
},
);
}
}

Answer 1

The issue is occurring because initialPosition is null until the late initialization occurs, but it is being converted to a non-nullable type before the late initialization occurs here: mapViewModel.initialPosition!.
You can resolve this one of two ways.
Return a default position if initialPosition is null when accessing it.
target: mapViewModel.initialPosition ?? [defaultPosition];
Display a loading widget until initialPosition is initialized, then display GoogleMap.
Both of these solutions will require a minor state management solution in order to update the widget when initialPosition is finally initialized.