方法 'requestWeather' 没有为类型 'AsyncValue' 定义

Question

我正在尝试了解 Flutter Riverpod。我可以从服务中获取和显示数据，并了解使用 AsyncValue 的好处。但是，当我尝试在应该调用 retrieveWeather 依次获取新位置的天气信息。但是我得到这个错误。

方法 'requestWeather' 没有为类型 'AsyncValue' 定义。尝试将名称更正为现有方法的名称，或定义名为 'requestWeather'.dartundefined_method

的方法

从 main.dart 我尝试使用 Provider 访问 requestWeather 函数。

    class InputLocationBox extends ConsumerWidget {
  String result = "";

  // final weatherListState = watch(weatherListControllerProvider);
  @override
  Widget build(BuildContext context, ScopedReader watch) {
    return Container(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          new TextField(
              decoration: new InputDecoration(hintText: "Type in here"),
              //onChanged is called whenever we add or delete something on Text Field
              onChanged: (String str) {
                result = str;
                // watch(weatherRepositoryProvider).retrieveWeather(location: str);
              }),
          //displaying input text
          new ElevatedButton(
            onPressed: () {
              context
                  .read(weatherListControllerProvider)
                  .requestWeather(location: result);
            },
            child: Text('Get user info'),
          )
        ],
      ),
    );
  }
}

Weather_list_controller.dart 定义了 requestWeather 函数。

 class WeatherListController extends StateNotifier<AsyncValue<Weather>> {
  final Reader _read;

  WeatherListController(this._read) : super(AsyncValue.loading()) {
    requestWeather();
  }

  Future<void> requestWeather({bool isRefreshing = false, String? loc}) async {
    if (isRefreshing) state = AsyncValue.loading();
    if (loc == null) {
      loc = 'Los Angeles';
    }

    try {
      final weathers =
          await _read(weatherRepositoryProvider).retrieveWeather(location: loc);
      if (mounted) {
        state = AsyncValue.data(weathers);
        // print(state);
      }
      // return weathers;
    } catch (e) {
      throw Exception(
          'Something went wrong in WeatherListController !! ' + e.toString());
    }
  }
}

Answer 1

当使用 StateNotifier 并尝试访问这些方法时，它需要 provider.notifier 像这样

context
              .read(weatherListControllerProvider.notifier)
              .requestWeather(loc: result);

我无法访问 requestWeather

的小部件

class InputLocationBox extends ConsumerWidget {
  String result = "";

  @override
  Widget build(BuildContext context, ScopedReader watch) {
    final weatherListState = watch(weatherListControllerProvider.notifier);
    return Container(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          new TextField(
              decoration: new InputDecoration(hintText: "Type in here"),
              //onChanged is called whenever we add or delete something on Text Field
              onChanged: (String str) {
                result = str;
                // watch(weatherRepositoryProvider).retrieveWeather(location: str);
              }),
          //displaying input text
          new ElevatedButton(
            onPressed: () {
              // context
              //     .read(weatherListControllerProvider)
              //     .requestWeather(location: result);
              print(result);
              context
                  .read(weatherListControllerProvider.notifier)
                  .requestWeather(loc: result);
            },
            child: Text('Get Weather'),
          )
        ],
      ),
    );
  }
}

方法 'requestWeather' 没有为类型 'AsyncValue' 定义

The method 'requestWeather' isn't defined for the type 'AsyncValue'

flutter

riverpod