Flutter Bloc 依赖项的多个侦听器 - 接收之前的状态

Question

这是我的 Flutter 应用程序 MultiBlocProvider 设置；

MultiBlocProvider(
      providers: [
        BlocProvider<LocationBloc>(create: (BuildContext context) {
          return LocationBloc();
        }),

        BlocProvider<AddressBloc>(create: (BuildContext context) {
          return AddressBloc(
              location: BlocProvider.of<LocationBloc>(context)
                ..add(LocationStarted()))
            ..add(AddressStarted());
        }),

        BlocProvider<CampaignBloc>(
          create: (BuildContext context) => CampaignBloc(
              addressBloc: BlocProvider.of<AddressBloc>(context),
              repo: CampaignsRepository())
            ..add(CampaignsInitial()),
        ),

        BlocProvider<BusinessBloc>(
          create: (BuildContext context) => BusinessBloc(
              addressBloc: BlocProvider.of<AddressBloc>(context),
              repo: BusinessRepository())
            ..add(BusinessInitial()),
        )
      ],
      child: MaterialApp(...)
          ,
    )

LocationBloc 从位置服务获取位置。AddressBloc 从 LocationBloc 获取更新的位置并将其转换为地址。

CampaignBloc 在其构造函数中侦听 AddressBloc 流以了解地址（位置）更改，并针对更改的位置发出营销活动。

CampaignBloc({required this.repo, required this.addressBloc})
      : super(CampaignState()) {
    _addressSubscription =
        addressBloc.stream.asBroadcastStream().listen((AddressState state) {
      if (state is AddressLoadSuccess) {
        Location location = state.location;

        add(CampaignChangedLocation(location: location));
      }
    });
  }

BusinessBloc 在其构造函数中执行相同的操作，并且（应该）为更改后的位置发出业务。

 BusinessBloc({required this.repo, required this.addressBloc})
      : super(BusinessInitial()) {
    _addressSubscription =
        addressBloc.stream.asBroadcastStream().listen((AddressState state) {
      if (state is AddressLoadSuccess) {
        Location location = state.location;

        add(BusinessChangedLocation(location: location));
      }
    });
  }

HomeView 有一个 BlocBuilder<CampaignBloc, CampaignState> 用于构建营销活动列表。

AlliesView 有一个 BlocBuilder<BusinessBloc, BusinessState> 用于构建企业列表。

CampaignBloc 在构建 HomeView 时接收更新的位置，但在转换到 AlliesView 时，AddressBloc 流上的侦听器不会接收更新的位置，因为它已在事件发生后订阅了该流。如何在 AddressBloc 流的后续侦听器中获取更新的位置？

Answer 1

MultiBlocListener(
  listeners: [
    BlocListener<BlocA, BlocAState>(
      listener: (context, state) {},
    ),
    BlocListener<BlocB, BlocBState>(
      listener: (context, state) {},
    ),
    BlocListener<BlocC, BlocCState>(
      listener: (context, state) {},
    ),
  ],
  child: ChildA(),
)