I want to display tatausaha data but every time I log in I get an error message "type null is not a subtype of type string", even though I use strings in my model and in firebase. can anyone help me?

this is my home_page.dart

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

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  void initState() {
    context.read<TataUsahaCubit>().fetchTataUsaha();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    Widget header() {
      return BlocBuilder<AuthCubit, AuthState>(
        builder: (context, state) {
          if (state is AuthSuccess) {
            return Container(
              margin: EdgeInsets.only(
                  right: defaultMargin, left: defaultMargin, top: 30),
              child: Row(
                children: [
                  Expanded(
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text(
                          'Hay,\n${state.user.name}',
                          style: blackTextStyle.copyWith(
                            fontSize: 24,
                            fontWeight: semiBold,
                          ),
                          overflow: TextOverflow.ellipsis,
                        ),
                        Text(
                          'Ingin Melihat Guru kamu?',
                          style: greyTextStyle.copyWith(
                            fontSize: 16,
                            fontWeight: light,
                          ),
                        ),
                      ],
                    ),
                  ),
                ],
              ),
            );
          } else {
            return SizedBox();
          }
        },
      );
    }

    Widget kepalaSekolah() {
      return Container(
        margin: EdgeInsets.only(
          left: defaultMargin,
          right: defaultMargin,
          top: 30,
        ),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              'Kepala Sekolah',
              style: blackTextStyle.copyWith(
                fontSize: 18,
                fontWeight: semiBold,
              ),
            ),
            KepalaSekolahTile(
              name: 'Charles Marsel Palasa, S.Pd.',
              imageUrl: 'assets/kepala_sekolah.jpeg',
              jabatan: 'Kepala Sekolah',
            ),
          ],
        ),
      );
    }

    Widget tataUsaha(List<TataUsahaModel> tatausahah) {
      return Container(
        margin: EdgeInsets.only(
          left: defaultMargin,
          right: defaultMargin,
          top: 20,
        ),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              'Tata Usaha',
              style: blackTextStyle.copyWith(
                fontSize: 18,
                fontWeight: semiBold,
              ),
            ),
            Column(
              children: tatausahah.map((TataUsahaModel tatausaha) {
                return TataUsahaTile(tatausaha);
              }).toList(),
            ),
          ],
        ),
      );
    }

    return BlocConsumer<TataUsahaCubit, TataUsahaState>(
        listener: (context, state) {
      if (state is TataUsahaFailed) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(
            backgroundColor: kRedColor,
            content: Text(state.error),
          ),
        );
      }
    }, builder: (context, state) {
      if (state is TataUsahaSuccess) {
        return ListView(
          children: [
            header(),
            kepalaSekolah(),
            tataUsaha(state.tatausahah),
          ],
        );
      }
      return Center(
        child: CircularProgressIndicator(
          color: kPrimaryColor,
        ),
      );
    });
  }
}

tata_usaha_cubit.dart

part 'tata_usaha_state.dart';

class TataUsahaCubit extends Cubit<TataUsahaState> {
  TataUsahaCubit() : super(TataUsahaInitial());
  void fetchTataUsaha() async {
    try {
      emit(TataUsahaLoading());

      List<TataUsahaModel> tatausahah =
          await TataUsahaService().fetchTataUsaha();
      emit(TataUsahaSuccess(tatausahah));
    } catch (e) {
      emit(TataUsahaFailed(e.toString()));
    }
  }
}

tata_usaha_state.dart

part of 'tata_usaha_cubit.dart';

abstract class TataUsahaState extends Equatable {
  const TataUsahaState();

  @override
  List<Object> get props => [];
}

class TataUsahaInitial extends TataUsahaState {}

class TataUsahaLoading extends TataUsahaState {}

class TataUsahaSuccess extends TataUsahaState {
  final List<TataUsahaModel> tatausahah;
  TataUsahaSuccess(this.tatausahah);
  @override
  List<Object> get props => [tatausahah];
}

class TataUsahaFailed extends TataUsahaState {
  final String error;
  TataUsahaFailed(this.error);
  @override
  List<Object> get props => [error];
}

tata_usaha_model.dart

import 'package:equatable/equatable.dart';

class TataUsahaModel extends Equatable {
  final String id;
  final String name;
  final String tahunMasuk;
  final String posisi;
  final String quotes;
  final String imageUrl;

  TataUsahaModel({
    required this.id,
    this.name = '',
    this.tahunMasuk = '',
    this.posisi = '',
    this.quotes = '',
    this.imageUrl = '',
  });

  factory TataUsahaModel.fromJson(String id, Map<String, dynamic> json) =>
      TataUsahaModel(
        id: id,
        name: json['name'],
        tahunMasuk: json['tahunMasuk'],
        posisi: json['posisi'],
        quotes: json['qoutes'],
        imageUrl: json['imageUrl'],
      );

  Map<String, dynamic> toJson() => {
        'id': id,
        'name': name,
        'tahunMasuk': tahunMasuk,
        'posisi': posisi,
        'quotes': quotes,
        'imageUrl': imageUrl,
      };

  @override
  List<Object?> get props => [
        id,
        name,
        tahunMasuk,
        posisi,
        quotes,
        imageUrl,
      ];
}

tata_usaha_service.dart

class TataUsahaService {
  CollectionReference _tatausahaRef =
      FirebaseFirestore.instance.collection('tatausaha');

  Future<List<TataUsahaModel>> fetchTataUsaha() async {
    try {
      QuerySnapshot result = await _tatausahaRef.get();

      List<TataUsahaModel> tatausaha = result.docs.map((e) {
        return TataUsahaModel.fromJson(e.id, e.data() as Map<String, dynamic>);
      }).toList();
      print(tatausaha);
      return tatausaha;
    } catch (e) {
      throw e;
    }
  }
}

CodePudding user response：

Please check your error message when building the app.

I don't know exactly where but, there is trying to parse String from null.

I guess the below part is the problem. (Not sure)

Text(
   'Hay,\n${state.user.name}',

Print the 'state.user.name' before you use it.

And make if condition to avoid it.

CodePudding user response：

You have to null safety. For example, you declare name is String then

name: json['name'] ?? ''; // default if null name will be set to empty

on another way: declare variable name as String? // ? means can be null.

or more carefully

name: (json['name'] ?? '').toString();
// eventhough server/firebase return wrong type such as Bool not String, your code will not be through exception wrong type casting.