firebase 存储的图像 link 正在返回 null - Flutter

Question

在显示图像的 fiorebase 存储 link 时，出现此错误 network_image_web.dart:26:16 url != null 不正确

下面是示例。是的，除了 pic

之外，提供者正在处理所有其他字段

class AddAlreadyExistingProductsView extends StatefulWidget {
  @override
  _AddAlreadyExistingProductsViewState createState() =>
      _AddAlreadyExistingProductsViewState();
}

class _AddAlreadyExistingProductsViewState
    extends State<AddAlreadyExistingProductsView> {
@override
  Widget build(BuildContext context) {
final _productsList = Provider.of<List<Product>>(context);

return Scaffold(
............
    child: 
       SearchableDropdown.single(
       ............
            items: _productsList.map((value) {
               print("---> pic : " + value.pic.toString()); // <--- NULL HERE
          ..........        
       child: ListTile(
             leading: CircleAvatar(
               backgroundImage: NetworkImage(value.pic),
            ),
           subtitle: Text(value.name)
.............
                                ) 
                             )
                            }

class MainDataProvider extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
       StreamProvider<List<Product>>.value(
        value: DatabaseService().getAllProducts,
........
      ],
      child: MaterialApp(
        home: AddAlreadyExistingProductsView (),
      ),
    );
  }
}

我也试过打印，打印图片的时候返回null。检索所有其他字段都可以。我在网络图像中给出了存储在 firebase 数据库中的图像的静态值，它工作正常。但是在动态获取数据时它不起作用。我不知道为什么。我在移动设备上以相同的方式获取数据并且它有效但对于 flutter web 它不起作用。

这是产品型号代码

  Stream<List<Product>> get getAllProducts {
    return productCollection.get().asStream().map(_productDataFromSnapshot);
  }

  List<Product> _productDataFromSnapshot(QuerySnapshot snapshot) {
    List<Product> productsList = List<Product>();

    for (int i = 0; i < snapshot.docs.length; i++) {
      productsList.add(Product(
        productID: snapshot.docs[i].data()['productID'] ?? "",
        name: snapshot.docs[i].data()['name'] ?? "",
        volume: snapshot.docs[i].data()['volume'] ?? "",
        price: snapshot.docs[i].data()['price'] ?? "",
        quantity: snapshot.docs[i].data()['quantity'] ?? "",
        brand: snapshot.docs[i].data()['brand'] ?? "",
        productAttribute: snapshot.docs[i].data()['productAttribute'] ?? "",
        productCtgName: snapshot.docs[i].data()['productCtgName'] ?? "",
        productSubCtgName: snapshot.docs[i].data()['productSubCtgName'] ?? "",
        productCtgID: snapshot.docs[i].data()['productCtgID'] ?? "",
        productSubCtgID: snapshot.docs[i].data()['productSubCtgID'] ?? "",
      ));
    }
    return productsList;
  }


class Product {
  String productID;
  String name;
  int price;
  int salePrice;
  DateTime addDate;
  String volume;
  int quantity;
  String productAttribute;
  String productSubCtgID;
  String productCtgID;
  String productSubCtgName;
  String productCtgName;
  String brand;
  String pic;

  Product({
    this.productID,
    this.name,
    this.price,
    this.addDate,
    this.volume,
    this.quantity,
    this.productAttribute,
    this.brand,
    this.productCtgID,
    this.productSubCtgID,
    this.productCtgName,
    this.productSubCtgName,
    this.pic,
    this.salePrice,
  });

Answer 1

在 for 循环的 _productDataFromSnapshot 函数中，您没有初始化 pic 字段。

为防止此类错误，请对此类字段使用@required

firebase 存储的图像 link 正在返回 null - Flutter

Image link of firebase storage is returning null - Flutter

image

flutter

firebase-storage

google-cloud-firestore

flutter-web