这网址显示错误给我铸造错误.我正在使用实时数据库和我也使用

{
  "rules": {
    "Products": {
      ".read": "auth != null",
      ".write": "auth != null"
    }

  }
}

当我添加数据时，数据保存在应用程序中，但post request未将其保存在firebase中我创建此应用程序表单acedemine course. URL正确。该URL可从您的我的位置或网络访问。服务器正在运行或维护。我想解决此问题，

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

import './product.dart';

class Products with ChangeNotifier {
  List<Product> _items = [
    Product(
      id: 'p1',
      title: 'Red Shirt',
      description: 'A red shirt - it is pretty red!',
      price: 29.99,
      imageUrl:
          'https://cdn.pixabay.com/photo/2016/10/02/22/17/red-t-shirt-1710578_1280.jpg',
    ),
    Product(
      id: 'p2',
      title: 'Trousers',
      description: 'A nice pair of trousers.',
      price: 59.99,
      imageUrl:
          'https://upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Trousers%2C_dress_%28AM_1960.022-8%29.jpg/512px-Trousers%2C_dress_%28AM_1960.022-8%29.jpg',
    ),
    Product(
      id: 'p3',
      title: 'Yellow Scarf',
      description: 'Warm and cozy - exactly what you need for the winter.',
      price: 19.99,
      imageUrl:
          'https://live.staticflickr.com/4043/4438260868_cc79b3369d_z.jpg',
    ),
    Product(
      id: 'p4',
      title: 'A Pan',
      description: 'Prepare any meal you want.',
      price: 49.99,
      imageUrl:
          'https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Cast-Iron-Pan.jpg/1024px-Cast-Iron-Pan.jpg',
    ),
  ];
 

  List<Product> get items {
 
    return [..._items];
  }

  List<Product> get favoriteItems {
    return _items.where((prodItem) => prodItem.isFavorite).toList();
  }

  get id => null;

  Product findById(String id) {
    return _items.firstWhere((prod) => prod.id == id);
  }


  void addProduct(Product product) {
    const url =
        "https://flutter-update-'this place is hide by me'firebasedatabase.app/Products.json";
    http.post(
      url ,
      body: json.encode({
        'title ': product.title,
        'description': product.description,
        'imageUrl': product.imageUrl,
        'price': product.price,
        'isFavorite': product.isFavorite
      }),
    );

    final newProduct = Product(
      title: product.title,
      description: product.description,
      price: product.price,
      imageUrl: product.imageUrl,
      id: DateTime.now().toString(),
    );
    _items.add(newProduct);

    notifyListeners();
  }

  void updateProduct(String id, Product newProduct) {
    final prodIndex = _items.indexWhere((prod) => prod.id == id);
    if (prodIndex >= 0) {
      _items[prodIndex] = newProduct;
      notifyListeners();
    } else {
      print('...');
    }
  }

  void deleteProduct(String id) {
    _items.removeWhere((prod) => prod.id == id);
    notifyListeners();
  }
}