Flutter 发生异常。NoSuchMethodError（NoSuchMethodError:getter'；documents'；在null上被调用。接收方：null尝试调用：documents）

我有两页。当我导航到另一个页面时，它有两个小部件，即类别和产品

class HomeScreen extends StatelessWidget {
  static String routeName = "/home";
  final DocumentSnapshot documentID;

  const HomeScreen({Key key, @required this.documentID}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        Provider<DocumentSnapshot>(create: (context) {
          return documentID;
        }),
        ChangeNotifierProvider<NewId>(create: (context) {
          return NewId();
        })
      ],
      child: new Scaffold(
        backgroundColor: Colors.white,
        body: Body(),
      ),
    );
  }
}

class Body extends StatelessWidget {
  // final DocumentSnapshot documentSnapshot;

  // const Body({Key key, @required this.documentSnapshot}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: SingleChildScrollView(
        child: Column(
          children: [
            SizedBox(height: getProportionateScreenHeight(20)),
            HomeHeader(),
            SizedBox(height: getProportionateScreenWidth(5)),
            DiscountBanner(),
            Categories(
                // documentSnapshot: documentSnapshot,
                ),
            //SpecialOffers(),
            SizedBox(height: getProportionateScreenWidth(15)),
            PopularProducts(),
            SizedBox(height: getProportionateScreenWidth(30)),
          ],
        ),
      ),
    );
  }
}

问题是当我从第一页传递navigate时，它显示为get文档被调用为null。到目前为止，我需要在索引[0]中显示产品的初始文档。但我不能将该文档作为一个价值来提及，因为我的产品和类别因公司而异。数据是通过firestore生成的。因为我的结构就像公司里有产品类别一样，在产品类别里有产品

class Categories extends StatefulWidget {
  // final DocumentSnapshot documentSnapshot;

  // const Categories({Key key, @required this.documentSnapshot})
  //     : super(key: key);
  @override
  _CategoriesState createState() => _CategoriesState();
}

class _CategoriesState extends State<Categories> {
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
  }

  @override
  void dispose() {
    // TODO: implement dispose
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return StreamBuilder(
        stream: FirebaseFirestore.instance
            .collection("Company-Master")
            .doc(Provider.of<DocumentSnapshot>(context).id)
            .collection("Products")
            .snapshots(),
        builder: (context, snapshot) {
          if (!snapshot.hasData) {
            return Center(
              child: CircularProgressIndicator.adaptive(),
            );
          }
          return Padding(
            padding: EdgeInsets.symmetric(horizontal: 10),
            child: Container(
              height: 90,
              width: double.infinity,
              child: ListView.builder(
                shrinkWrap: true,
                physics: AlwaysScrollableScrollPhysics(),
                scrollDirection: Axis.horizontal,
                itemCount: snapshot.data.documents.length,
                itemBuilder: (context, index) {
                  return Padding(
                    padding: EdgeInsets.symmetric(horizontal: 8),
                    child: CategoryCard(
                      icon: snapshot.data.documents[index]["PCategoryImage"],
                      text: snapshot.data.documents[index]["PCategoryName"],
                      press: () {
                        setState(() {
                          Provider.of<NewId>(context, listen: false)
                              .changeDocumentID(snapshot.data.documents[index]);
                        });
                      },
                    ),
                  );
                },
              ),
            ),
          );
        });
  }
}

class CategoryCard extends StatelessWidget {
  const CategoryCard({
    Key key,
    @required this.icon,
    @required this.text,
    this.press,
    this.description,
  }) : super(key: key);

  final String icon, text, description;
  final GestureTapCallback press;

  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: press,
      hoverColor: kTextColor,
      child: SizedBox(
        width: getProportionateScreenWidth(55),
        child: Column(
          children: [
            Container(
              padding: EdgeInsets.all(getProportionateScreenWidth(15)),
              height: getProportionateScreenWidth(55),
              width: getProportionateScreenWidth(55),
              decoration: BoxDecoration(
                color: Color(0xFFFFECDF),
                borderRadius: BorderRadius.circular(10),
              ),
              child: SvgPicture.network(icon),
            ),
            SizedBox(height: 5),
            Text(
              text,
              textAlign: TextAlign.center,
              style: TextStyle(fontSize: getProportionateScreenWidth(10)),
            )
          ],
        ),
      ),
    );
  }
}

class PopularProducts extends StatelessWidget {
  final String getID;

  const PopularProducts({Key key, this.getID}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return StreamBuilder(
        stream: FirebaseFirestore.instance
            .collection("Company-Master")
            .doc(Provider.of<DocumentSnapshot>(context).id)
            .collection("Products")
            .doc(Provider.of<NewId>(context).id)
            .collection("Products")
            .snapshots(),
        builder: (context, snapshot) {
          if (!snapshot.hasData) {
            Center(
              child: CircularProgressIndicator(),
            );
          }
          if (snapshot.data == null) {
            print("Fuck ya");
          }

          return Container(
            height: 600,
            child: ListView.builder(
              itemCount: snapshot.data.documents.length,
              itemBuilder: (context, index) {
                if (snapshot.data.documents[index] == null) {
                  Center(
                    child: Text("Choose a category to view products"),
                  );
                }
                return ProductListColumn(
                  productName: snapshot.data.documents[index]["ProductName"],
                );
              },
            ),
          );
        });
  }
}

class ProductListColumn extends StatelessWidget {
  const ProductListColumn({
    Key key,
    @required this.productName,
  }) : super(key: key);
  final String productName;

  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: () {
        Navigator.of(context).push(
          new MaterialPageRoute(
            builder: (BuildContext context) => new ProductDetailScreen(
              productName: productName,
            ),
            // snapshot.data.documents[index]['SubName'],
            // snapshot.data.documents[index].documentID),
          ),
        );
      },
      child: Stack(
        children: [
          Container(
            margin: EdgeInsets.all(10),
            decoration: BoxDecoration(
              color: Color(0xFFDECB9C),
              borderRadius: BorderRadius.circular(20),
            ),
            height: 130,
            width: double.infinity,
            child: Container(
              height: 130,
              decoration: BoxDecoration(
                boxShadow: [
                  BoxShadow(
                    color: Colors.white,
                  ),
                ],
                borderRadius: BorderRadius.circular(20),
              ),
              margin: EdgeInsets.only(right: 10, bottom: 5),
            ),
          ),
          Positioned(
            right: 30,
            bottom: 40,
            child: Container(
              height: 110,
              width: 110,
              decoration: BoxDecoration(
                color: Color(0xFFDECB9C),
                borderRadius: BorderRadius.circular(20),
              ),
              child: Image.asset(
                "assets/images/Image Popular Product 3.png",
                fit: BoxFit.cover,
              ),
            ),
          ),
          Positioned(
            left: 30,
            top: 60,
            child: Container(
              child: Text(
                productName,
                style: TextStyle(
                    fontSize: 14,
                    fontWeight: FontWeight.w600,
                    color: Colors.black),
              ),
            ),
          )
        ],
      ),
    );
  }
}

class NewId extends ChangeNotifier {
  String id;

  void changeDocumentID(DocumentSnapshot newID) {
    id = newID.id;
    notifyListeners();
  }