how can i get length of list in widget

Issue

I can’t get the length of the list in the widget although I wrote everything correct

this is my cubit

class AppCubit extends Cubit<NewsStates> {
  AppCubit() : super(NewsInit());

  static AppCubit get(context) => BlocProvider.of(context);
  MianTeams? mianTeams;
  void getTimes() {
    emit(NewsLoding());
    DioHelper.getData(
            Qurey: {"action": "get_teams", "league_id": "141", "APIkey": api})
        .then((value) {
      mianTeams = MianTeams.fromJson(value.data);
////////////////+++++  i can get the length here in cubit 
      print(mianTeams!.team.length);
  
      emit(NewsSucsess());
    }).catchError((onError) {
      print(onError.toString());
      emit(NewsErorr(onError.toString()));
    });
  }

this is my model

class MianTeams {
  List<TeamsModel> team = [];
  MianTeams.fromJson(List<dynamic> json) {
    json.forEach((e) {
      team.add(TeamsModel.fromJson(e));
    });
  }
}

class TeamsModel {
  String? teamKey;
  String? teamName;
  String? teamBadge;
  List<Players> players = [];
  TeamsModel.fromJson(Map<String, dynamic> json) {
    teamKey = json['team_key'];
    teamName = json['team_name'];
    teamBadge = json['team_badge'];
    json['players'].forEach((e) {
      players.add(Players.fromJson(e));
    });
  }
}

but in Widget I can’t get the length to set the itemCount of List View separated

this is my statelessWidget

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

  @override
  Widget build(BuildContext context) {
    return BlocConsumer<AppCubit, NewsStates>(
        listener: (context, state) {},
        builder: (context, state) {
          //  print(AppCubit.get(context).mianTeams!.team.length);          
          return Scaffold(
            appBar: AppBar(),
            body: ListView.separated(
                itemBuilder: (context, index) => Divider(),
                separatorBuilder: (context, index) => Divider(),
                itemCount: AppCubit.get(context).mianTeams!.team.length), 
          );
        });
  }
}

I don’t know what’s wrong and I think I wrote everything correctly

Solution

The problem is that mianTeams is null until after getTimes() is called and the response is received from your API. So when the ListView tries to build initially, it’s trying to get the length of a null list.

Instead of storing mianTeams directly as a property of the Cubit, you should make it a property of one of your State classes. Probably NewsSuccess – then the list will always be available in that state. And if the Cubit is in a different state, you can display a loading indicator or something.

Your Cubit might then look something like this:

class AppCubit extends Cubit<NewsStates> {
  AppCubit() : super(NewsInit());

  static AppCubit get(context) => BlocProvider.of(context);

  void getTimes() {
    emit(NewsLoding());
    DioHelper.getData(
            Qurey: {"action": "get_teams", "league_id": "141", "APIkey": api})
        .then((value) {
      final mianTeams = MianTeams.fromJson(value.data);
  
      emit(NewsSucsess(mianTeams: mianTeams));
    }).catchError((onError) {
      print(onError.toString());
      emit(NewsErorr(onError.toString()));
    });
  }
}

And your widget might be something like:

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

  @override
  Widget build(BuildContext context) {
    return BlocConsumer<AppCubit, NewsStates>(
        listener: (context, state) {},
        builder: (context, state) {        
          return Scaffold(
            appBar: AppBar(),
            body: _buildBody(state),
        });
  }

  Widget _buildBody(NewsStates state) {
    if (state is NewsError) {
      // For example
      return Text("Error: ${state.message}");
    } else if (state is NewsLoding) {
      // For example
      return const CircularProgressIndicator();
    } else if (state is NewsSuccess) {
      return ListView.separated(
          itemBuilder: (context, index) => Divider(),
          separatorBuilder: (context, index) => Divider(),
          itemCount: state.mianTeams.team.length), 
      );
    } else {
      // Handle any other possible states you have
    }
  }
}

Answered By – Michael Horn

Answer Checked By – Clifford M. (FlutterFixes Volunteer)