map_bloc.dart

class MapBloc extends Bloc<MapEvent, MapState> { ...
  Set<Marker> _markers = Set();

  Set<Marker> getMarkers() {
    return _markers;
  }
  ...
  
  @override
  Stream<MapState> mapEventToState(
    MapEvent event,
  ) async* {
    if (event is UpdateMarkersData) {
      _clusteringHelper.updateData(event.data);
      yield Redrawing();
    }
    if (event is MarkersUpdated) {
      yield Updated();
    }
    ...
      
      abstract class MapState extends Equatable {

  @override
  List<Object> get props => [];
}
      
      class Updated extends MapState {
}

class Redrawing extends MapState {
}
    ....
      
      
      Widget _map(BuildContext context) {
    return BlocBuilder<MapBloc, MapState>(builder: (context, state) {
      return GoogleMap(
        key: _keyMap,
        onMapCreated: (GoogleMapController controller) {
          _mapController = controller;
          BlocProvider.of<MapBloc>(context)
              .add(MapLoaded(mapController: controller));
        },
        myLocationEnabled: true,
        myLocationButtonEnabled: false,
        markers: BlocProvider.of<MapBloc>(context).getMarkers(),
        initialCameraPosition: CameraPosition(target: _center, zoom: 3.0),
        onCameraIdle: () => BlocProvider.of<MapBloc>(context).add(CameraIdle()),
        onCameraMove: (newPosition) => BlocProvider.of<MapBloc>(context)
            .add(CameraMove(position: newPosition)),
      );
    });
  }