从StreamBuilder BloC Firestore Flutter获取数据时出错

Question

我在Flutter中的APP一直存在问题...我试图从Bloc，Repositore和Firestore获取数据，并且该数据显示在GridView中，但出现此错误：

我的UI代码：

Widget bodyGallery2() => SafeArea(
    child: Scaffold(
      body: Stack(
        children: <Widget>[
          StreamBuilder<List<PhotoDish>>(
            stream: _dishBloc.streamPhotoDish,
            builder: (context, snapshot) {
              if (!snapshot.hasData) {
                return CircularProgressIndicator();
              }
              print(snapshot.toString());
              return GridView.count(
              crossAxisCount: 1,
              crossAxisSpacing: 4.0,
              mainAxisSpacing: 8.0,
              childAspectRatio: 3/2,
              children: snapshot.data
                    .map((photo)=>buildItemPhoto(photo)),
              );
            }
      )
        ]
    ),
    ),
  );

  Widget buildItemPhoto(PhotoDish listphoto){
    return Text(listphoto.idDish+":::PhotoDish");
  }

我的集团代码，它具有从我的存储库中流到PhotoDish的列表：

class DishBloc extends Bloc{ 
  RepositoryFirestore _repository = RepositoryFirestore();

  PhotoDishRepo _repo = FirestoreDishProvider();
  Stream<List<PhotoDish>> get streamPhotoDish => _repo.streamPhotoDish;

我的回购代码已调用从Firebase获取数据，并在StreamController中进行了设置：

abstract class PhotoDishRepo {
  Stream<List<PhotoDish>> get streamPhotoDish;
}
class FirestoreDishProvider implements PhotoDishRepo{
  StreamController<List<PhotoDish>> _streamController = BehaviorSubject<List<PhotoDish>>();

  Firestore _firestore = Firestore.instance;
  List<PhotoDish> _listPhotoDish = List();

  FirestoreDishProvider() {

    _firestore
      .collection(Constants.namePhotoDishCollection) 
      .snapshots()
      .listen((QuerySnapshot snapshot){
        snapshot.documents.forEach((obj){
          _listPhotoDish.add(PhotoDish(
            date: DateTime.now(),
            id: obj.data["id"],
            idDish: obj.data["idDish"],
            idUser: obj.data["idUser"],
            photo: obj.data["photo"],
          ));
        });

print("TOTALL:::"+_listPhotoDish.length.toString());
        _streamController.add(_listPhotoDish);
      });
  }

Answer 1

我认为您只是想念在将列表映射到小部件的末尾添加.ToList（）方法。