Null check operator used on a null value issue in flutter

Question

I have the issue of _CastError (Null check operator used on a null value, its happened in openstreet map included in Flutter project when i choose service of car in rider app and greate reuest of ride.

check the code :

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:graphql_flutter/graphql_flutter.dart';
import 'package:ridy/generated/l10n.dart';
import '../graphql/generated/graphql_api.dart';
import 'bloc/main_bloc.dart';
import '../main/select_service_view.dart';
import 'package:velocity_x/velocity_x.dart';

class ServiceSelectionCardView extends StatelessWidget {
  const ServiceSelectionCardView({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final mainBloc = context.read<MainBloc>();
    return BlocBuilder<MainBloc, MainBlocState>(builder: (context, state) {
      return Mutation(
        options: MutationOptions(document: CREATE_ORDER_MUTATION_DOCUMENT),
        builder: (RunMutation runMutation, QueryResult? result) {
          return Column(
            children: [
              FloatingActionButton.extended(
                      heroTag: 'cancelFab',
                      onPressed: () => mainBloc.add(ResetState()),
                      label: Text(S.of(context).action_cancel),
                      icon: const Icon(Icons.close))
                  .pOnly(bottom: 8)
                  .objectCenterRight(),
              SelectServiceView(
                data: (state as OrderPreview).fareResult,
                onServiceSelect: (String serviceId, int intervalMinutes) async {
                  final args = CreateOrderArguments(
                          input: CreateOrderInput(
                              serviceId: int.parse(serviceId),
                              intervalMinutes: 0,
                              points: state.points
                                  .map((e) => PointInput(
                                      lat: e.point.latitude,
                                      lng: e.point.longitude))
                                  .toList(),
                              addresses:
                                  state.points.map((e) => e.address).toList()))
                      .toJson();
                  final result = await runMutation(args).networkResult;
                  //print(result!.data!.toString());
                  final _order =
                      CreateOrder$Mutation.fromJson(result!.data!).createOrder;
                  mainBloc.add(OrderUpdated(order: _order));
                },
              ),
            ],
          );
        },
      );
    });
  }
}

see this screenshot :

Answer 1

Try using the bang operator !, when you're 100% sure that the variable can't be null. Seems like result.data can in fact be null, if you log the result you will see that this is the case. You can try making a null check first before serializing the response :

if (result!=null){
 if (result!.data!=null){
  // result.data here is never `null`
 }
}

Answer 2

Change this line

 CreateOrder$Mutation.fromJson(result!.data!).createOrder;

with this one

 CreateOrder$Mutation.fromJson(result.data).createOrder;

Answer 3

Try below hope its help to you.you have put extra ! null operator remove it. Refer Flutter Sound null safety here and here

Replace

result!.data!

to this

result!.data

Full declaration:

final _order = CreateOrder$Mutation.fromJson(result!.data).createOrder;
                  mainBloc.add(OrderUpdated(order: _order));