当我使用 http.get() 从 API 获取数据时出现错误

Question

我在我的代码中遇到了这个问题，但我无法解决它。我正在尝试通过 API 获取数据，但我在 IDE.

中遇到了这些错误

    [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: type 'Null' is not a subtype of type 'String'
#0      Products.fetchAndSetProducts.<anonymous closure> (package:shop_app/providers/products_provider.dart:85:28)
#1      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:400:8)
#2      Products.fetchAndSetProducts (package:shop_app/providers/products_provider.dart:81:21) <asynchronous suspension>

以上错误指向此函数

Future<void> fetchAndSetProducts() async {
    final url = Uri.parse(
      'https://flutter-update-607c9-default-rtdb.firebaseio.com/products.json',
    );
    try {
      final response = await http.get(url);
      final extractedData = json.decode(response.body) as Map<String, dynamic>;
      final List<Product> loadedProducts = [];
      extractedData.forEach((prodId, prodData) {
        loadedProducts.add(
          Product(
            id: prodId,
            title: prodData['title'],
            description: prodData['description'],
            price: prodData['price'],
            isFavorite: prodData['isFavorite'],
            imageUrl: prodData['imageUrl'],
          ),
        );
      });
      _items = loadedProducts;
      notifyListeners();
    } catch (error) {
      rethrow;
    }
  }

这是我的产品class

class Product with ChangeNotifier {
  final String? id;
  final String title;
  final String description;
  final double price;
  final String imageUrl;
  bool isFavorite;

  Product(
      {required this.id,
      required this.title,
      required this.description,
      required this.price,
      required this.imageUrl,
      this.isFavorite = false});
}

如有任何帮助，我们将不胜感激！

Answer 1

JSON at the URL 中的最后一个条目看起来与其他条目不同：.

{
  "-MxpO80SMxlqxMs6Q2-O" : {
    "description" : "is this long enough for you",
    "imageUrl" : "https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Cast-Iron-Pan.jpg/1024px-Cast-Iron-Pan.jpg",
    "isFavorite" : true,
    "price" : 420.99,
    "title" : "pan"
  },
  "-MxxqC8KwLPlgsmWBITe" : {
    "description" : "this is a test long one",
    "imageUrl" : "https://live.staticflickr.com/4043/4438260868_cc79b3369d_z.jpg",
    "isFavorite" : true,
    "price" : 12.0,
    "title" : "Yellow scarf"
  },
  "-MySBTTTKRTj4jXzAlhA" : {
    "amount" : 12.0,
    "dateTime" : "2022-03-18T15:22:46.740475",
    "products" : [ {
      "id" : "2022-03-18 15:22:43.791990",
      "price" : 12.0,
      "quantity" : 1,
      "title" : "Yellow scarf"
    } ]
  }
}

虽然 Firebase 可以处理无模式数据，但您的代码希望每个 child 节点都具有某些属性，并且 -MySBTTTKRTj4jXzAlhA 节点没有 ID、标题、描述，imageUrl ，或您尝试阅读的任何其他属性。

当我使用 http.get() 从 API 获取数据时出现错误

i get errors when I fetch my data from an API using http.get()

dart

firebase-realtime-database

flutter

flutter-dependencies

dart-null-safety