Flutter Bloc 和 Http Library bloc 状态未更新

Question

我使用 bloc 8.0.1 和 http ^0.13.4。

当您运行应用程序时，屏幕上只会显示 WeatherInitial() 状态。我看不到其他州。 debugPrint("debug3"); 我在控制台中看不到这行代码。 try catch 不在代码行内。你能找出问题所在吗？

集团

class WeatherBloc extends Bloc<WeatherEvent, WeatherState> {
final WeatherRepository repository = locator<WeatherRepository>();

WeatherBloc() : super(WeatherInitial()) {
  on<WeatherEvent>((event, emit) async {
   if (event is FetchWeatherEvent) {
     WeatherLoadingState();
    try {
     final Weather? weather = await repository.getWeather(event.cityName);
      WeatherLoadedState(weather: weather!);
      debugPrint("debug3");
     } catch (_) {
      WeatherErrorState();
    }
   }
  });
  }
}

事件

 abstract class WeatherEvent extends Equatable {
 const WeatherEvent();

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

 class FetchWeatherEvent extends WeatherEvent {
  final String cityName;

 const FetchWeatherEvent({required this.cityName});
}

州

 abstract class WeatherState extends Equatable {
  const WeatherState();

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

 class WeatherInitial extends WeatherState {}

 class WeatherLoadingState extends WeatherState {}

 class WeatherLoadedState extends WeatherState {
  final Weather weather;

const WeatherLoadedState({required this.weather});
 }
class WeatherErrorState extends WeatherState {}

正文

 class WeatherApp extends StatelessWidget {
     String? selectedCity;
    @override
     Widget build(BuildContext context) {
    final _weatherBloc = BlocProvider.of<WeatherBloc>(context);
    return Scaffold(
     appBar: AppBar(
       title: const Text("WeatherApp"),
        actions: [
       IconButton(
        onPressed: () async {
          selectedCity = await Navigator.of(context).push(
            MaterialPageRoute(
              builder: (context) => const CityChoose(),
            ),
          );
          if (selectedCity != null) {
            _weatherBloc.add(FetchWeatherEvent(cityName: 
     selectedCity!));
          }
        },
        icon: const Icon(Icons.search),
      ),
     ],
    ),
   body: Center(
    child: BlocBuilder(
      bloc: _weatherBloc,
      builder: (context, WeatherState state) {
        if (state is WeatherInitial) {
          return const Center(
            child: Text("Select City"),
          );
        } 
         if (state is WeatherLoadingState) {
          return const Center(
            child: CircularProgressIndicator(),
          );
        } 
         if (state is WeatherLoadedState) {
          final weather = state.weather;
          debugPrint(weather.title);
          return ListView(
            children: [
              Padding(
                padding: const EdgeInsets.all(8.0),
                child: Center(
                    child: LocationWidget(
                  selectedCity: weather.title,
                )),
              ),
              const Padding(
                padding: EdgeInsets.all(8.0),
                child: Center(child: LastUpdateWidget()),
              ),
              const Padding(
                padding: EdgeInsets.all(8.0),
                child: Center(child: WeatherImageWiddget()),
              ),
              const Padding(
                padding: EdgeInsets.all(16.0),
                child: Center(child: TemperatureCondition()),
              ),
            ],
          );
        } else {
          return const Center(
            child: Text("Error"),
          );
        }
         },
        ),
      ),

Answer 1

您需要使用 emit 在 Bloc 中发出一个状态。 emit 在 on<T>.

的闭包中声明

emit(WeatherLoadedState(weather: weather!));
emit(WeatherErrorState());

Flutter Bloc 和 Http Library bloc 状态未更新

Flutter Bloc and Http Library bloc state not updating

flutter

bloc