如何从另一个块访问块状态中的数据

我正在使用 Bloc 模式开发 Flutter 应用程序。认证成功后，UserSate就有了User对象。在所有其他 Bloc 中，我需要访问 UserState 中的 User 对象。我尝试在其他 Bloc 的构造函数参数上获取 UserBloc 并访问 User 对象。但它显示 User 对象为 null。有人有更好的解决方案吗？

class SectorHomeBloc extends Bloc<SectorHomeEvent, SectorHomeState> {
  final OutletRepository outletRepository;
  UserBloc userBloc;
  final ProductRepository productRepository;
  final ProductSubCategoryRepository productSubCategoryRepository;
  final PromotionRepository promotionRepository;
  final ProductMainCategoryRepository mainCategoryRepository;

  SectorHomeBloc({
    @required this.outletRepository,
    @required this.userBloc,
    @required this.productSubCategoryRepository,
    @required this.productRepository,
    @required this.promotionRepository,
    @required this.mainCategoryRepository,
  });
  @override
  SectorHomeState get initialState => SectorHomeLoadingState();

  @override
  Stream<SectorHomeState> mapEventToState(SectorHomeEvent event) async* {
    try {
      print(userBloc.state.toString());
      LatLng _location = LatLng(
          userBloc.state.user.defaultLocation.coordinate.latitude,
          userBloc.state.user.defaultLocation.coordinate.longitude);
      String _token = userBloc.state.user.token;

      if (event is GetAllDataEvent) {
        yield SectorHomeLoadingState();
        List<Outlet> _previousOrderedOutlets =
            await outletRepository.getPreviousOrderedOutlets(
                _token, _location, event.orderType, event.sectorId);

        List<Outlet> _featuredOutlets =
            await outletRepository.getFeaturedOutlets(
                _token, _location, event.orderType, event.sectorId);
        List<Outlet> _nearestOutlets = await outletRepository.getOutletsNearYou(
            _token, _location, event.orderType, event.sectorId);

        List<Product> _newProducts = await productRepository.getNewItems(
            _token, _location, event.orderType, event.sectorId);

        List<Product> _trendingProducts =
            await productRepository.getTrendingItems(
                _token, _location, event.orderType, event.sectorId);

        List<Promotion> _promotions = await promotionRepository
            .getVendorPromotions(_token, event.sectorId);
        yield SectorHomeState(
          previousOrderedOutlets: _previousOrderedOutlets,
          featuredOutlets: _featuredOutlets,
          nearByOutlets: _nearestOutlets,
          newItems: _newProducts,
          trendingItems: _trendingProducts,
          promotions: _promotions,
        );
      }
    } on SocketException {
      yield SectorHomeLoadingErrorState('could not connect to server');
    } catch (e) {
      print(e);
      yield SectorHomeLoadingErrorState('Error');
    }
  }
}

mapEventToState方法中的打印语句[print(userBloc.state.toString());]显示了UserSate的初始状态。 但是，在执行此代码时，UserState 处于 UserLoggedInState 状态。

更新（最佳实践）： 请参阅在这里回答 https://stackoverflow.com/a/72528313/6896271因此，最好的方法是听取您所在小部件内另一个块的更改，并根据该更改触发事件。 所以你要做的就是将你的小部件包装在一个块监听器中并监听你想要的块。

    class SecondPage extends StatelessWidget {
      const SecondPage({Key? key}) : super(key: key);
    
      @override
      Widget build(BuildContext context) {
        return BlocListener<FirstBloc, FirstBlocState>(
          listener: (context, state) {
             if(state is StateFromFirstBloc){
             BlocProvider.of<SecondBloc>(context).add(SecondBlocEvent());}//or whatever you want
          },
          child: ElevatedButton(
            child:   Text('THIS IS NEW SCREEN'),
            onPressed: () {
              BlocProvider.of<SecondBloC>(context).add(SecondBloCEvent());
            },
          ),
        );
      }
    }

监听器的可爱之处在于你可以在任何地方监听任何集团并做任何你想做的事情 这里是官方文档 https://bloclibrary.dev/#/architecture?id=bloc-to-bloc-communication for it

老方法（不推荐）

有一种官方方法可以做到这一点，如文档中所示，称为块对块通信 https://bloclibrary.dev/#/architecture?id=bloc-to-bloc-communication这是文档中的示例

class MyBloc extends Bloc {
  final OtherBloc otherBloc;
  StreamSubscription otherBlocSubscription;

  MyBloc(this.otherBloc) {
    otherBlocSubscription = otherBloc.listen((state) {
        // React to state changes here.
        // Add events here to trigger changes in MyBloc.
    });
  }

  @override
  Future<void> close() {
    otherBlocSubscription.cancel();
    return super.close();
  }
}

抱歉这个答案更新较晚，感谢@MJ studio