Flutter : The getter 'length' was called on null

Question

I have this error and i don't know what's wrong

════════ Exception caught by widgets library ═══════════════════════════════════ The following NoSuchMethodError was thrown building HomeScreen(dirty, dependencies: [_InheritedProviderScope, MediaQuery], state: _HomeScreenState#1d9fe): The getter 'length' was called on null. Receiver: null Tried calling: length The relevant error-causing widget was HomeScreen lib\…\View\login.dart:387 When the exception was thrown, this was the stack #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5) #1 _HomeScreenState.build package:chroma/…/resident/home.dart:61 #2 StatefulElement.build package:flutter/…/widgets/framework.dart:4744 #3 ComponentElement.performRebuild package:flutter/…/widgets/framework.dart:4627 #4 StatefulElement.performRebuild

I want to fetch data by using api service and show it in ListBuilder

ListView(
                      scrollDirection: Axis.vertical,
                      shrinkWrap: true,
                      physics: NeverScrollableScrollPhysics(),
                      children: [
                        GridView.builder(
                          gridDelegate:
                              SliverGridDelegateWithFixedCrossAxisCount(
                                  crossAxisCount: 2),
                          shrinkWrap: true,
                          scrollDirection: Axis.vertical,
                          itemCount: appProvider.homeService.length,
                          itemBuilder: (context, index) {
                            return HomeServiceList(
                              service: appProvider.homeService[index],
                              isShowDate: true,
                              callback: () {
                              },
                            );
                          },
                        ),
                      ],
                    ),

and this is the class of model

class Service {
  Service({
    this.id,
    this.name,
    this.homePhoto,
    this.subServices,
  });

  int id;
  String name;
  dynamic homePhoto;
  List<Service> subServices;

  factory Service.fromJson(Map<String, dynamic> json) => Service(
        id: json["id"],
        name: json["name"],
        homePhoto: json["home_photo"],
        subServices: List<Service>.from(
            json["sub_services"].map((x) => Service.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "name": name,
        "home_photo": homePhoto,
        "sub_services": List<dynamic>.from(subServices.map((x) => x.toJson())),
      };
}

and this is the function to call it

class AppProvider with ChangeNotifier {
  List<Service> _homeService;

  List<Service> get homeService => _homeService;

  bool _isLoading = false;
  bool get isLoading => _isLoading;

  set isLoading(bool value) {
    _isLoading = value;
    notifyListeners();
  }

  Future<dynamic> homeListService() async {
    _isLoading = true;
    notifyListeners();
    print('Starting request');

    http.Response response =
        await http.get(Environment.home, headers: Environment.requestHeader);
    print('Completed request');
    print('respond countryList data : ${response.body}');

    Map<String, dynamic> res = json.decode(response.body);
    var results;
    if (res['code'] == 200) {
      _homeService = [];
      res['services'].forEach((v) {
        _homeService.add(new Service.fromJson(v));
      });
      results = true;
    } else {
      results =
          FailedRequest(code: 400, message: res['massage'], status: false);
    }
    _isLoading = false;
    notifyListeners();
    return results;
  }
}

please, can anyone help me in my case !!!

Answer 1

Change itemCount: appProvider.homeService.length, to :

itemCount: appProvider.homeService?.length ?? 0,