问当我尝试this.in颤动时，我得到了这个错误。以前的版本我是这样构建的，但现在我不能。颤动快照映射

EN

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:hit_app/pages/HomePageViwe/Product.dart';

class DatabaseServise{
  final String uid;

  DatabaseServise({this.uid});
  
  //collection reference 
  final CollectionReference productsReference = FirebaseFirestore.instance.collection("products"); 

  //product list from snapshot
  List<Product> _productListFromSnapshot(QuerySnapshot snapshot){
    return snapshot.docs.map((e){
      return Product(
        name: e.data()["name"] ?? "",
        img : e.data()["Image"] ?? "",
        country: e.data()["Country"] ?? "",
        discription: e.data()["Description"] ?? "",
        mulImg: e.data()["multiimage"] ?? ""
      );
    }).toList();
  }

  //get product stream
  Stream<List<Product>> get products{
    return productsReference.snapshots().map(_productListFromSnapshot);
  }
}

 cupertino_icons: ^1.0.2
  firebase_auth: ^3.0.1
  cloud_firestore: ^2.4.0
  firebase_database: ^7.1.2
  crypto: ^3.0.1
  lottie: ^1.1.0
  flutter_svg: ^0.22.0
  flutter_signin_button: ^2.0.0
  fluttertoast: ^8.0.8
  image_picker: ^0.8.3+1
  image_cropper: ^1.4.1
  scoped_model: ^1.1.0
  firebase_storage: ^10.0.1
  geoflutterfire: ^3.0.1
  google_sign_in: ^5.0.7
  animate_do: ^2.0.0
  carousel_slider: ^4.0.0
  line_icons: ^2.0.1
  drop_cap_text: ^1.1.3
  font_awesome_flutter: ^9.1.0
  provider: ^5.0.0