【发布时间】：2023-02-05 21:28:22
【问题描述】：
我正在创建一个简单的 Shop 应用程序，我在其中实现了添加我们自己的产品以列出和更新列表中现有产品的逻辑。更新进行得非常顺利，但每当我尝试添加新产品时，应用程序有时会崩溃，有时结果会反映任何情况。
这是我的代码。除了 price (int) 之外，所有实体都是 String 类型。
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shop_app/provider/product.dart';
import 'package:shop_app/provider/product_provider.dart';
class EditProductScreen extends StatefulWidget {
static const routname = '/edit-product-screen';
const EditProductScreen({Key? key}) : super(key: key);
@override
State<EditProductScreen> createState() => _EditProductScreenState();
}
class _EditProductScreenState extends State<EditProductScreen> {
final _priceFocusNode = FocusNode();
final _descriptionFocusNode = FocusNode();
final _imageUrlController = TextEditingController();
final _imageUrlFocusNode = FocusNode();
final _form = GlobalKey<FormState>();
var _editedProduct = Product(
id: '',
title: '',
price: 0,
description: '',
imageUrl: '',
);
var _initValues = {
'title': '',
'description': '',
'price': '',
'imageUrl': '',
};
var _isInit = true;
@override
void initState() {
_imageUrlFocusNode.addListener(_updateImageUrl);
super.initState();
}
@override
void didChangeDependencies() {
if (_isInit) {
final productId = ModalRoute.of(context)!.settings.arguments;
// ignore: unnecessary_null_comparison
if (productId != null) {
_editedProduct = Provider.of<ProductsProvider>(context, listen: false)
.findById(productId.toString());
_initValues = {
'title': _editedProduct.title,
'description': _editedProduct.description,
'price': _editedProduct.price.toString(),
// 'imageUrl': _editedProduct.imageUrl,
'imageUrl': '',
};
_imageUrlController.text = _editedProduct.imageUrl;
}
}
_isInit = false;
super.didChangeDependencies();
}
@override
void dispose() {
_imageUrlFocusNode.removeListener(_updateImageUrl);
_priceFocusNode.dispose();
_descriptionFocusNode.dispose();
_imageUrlController.dispose();
_imageUrlFocusNode.dispose();
super.dispose();
}
void _updateImageUrl() {
if (!_imageUrlFocusNode.hasFocus) {
if ((!_imageUrlController.text.startsWith('http') &&
!_imageUrlController.text.startsWith('https')) ||
(!_imageUrlController.text.endsWith('.png') &&
!_imageUrlController.text.endsWith('.jpg') &&
!_imageUrlController.text.endsWith('.jpeg'))) {
return;
}
setState(() {});
}
}
void _saveForm() {
final isValid = _form.currentState!.validate();
if (!isValid) {
return;
}
_form.currentState!.save();
// ignore: unnecessary_null_comparison
if (_editedProduct.id != null) {
Provider.of<ProductsProvider>(context, listen: false)
.updateProduct(_editedProduct.id, _editedProduct);
} else {
Provider.of<ProductsProvider>(context, listen: true)
.addProduct(_editedProduct);
}
Navigator.of(context).pop();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Edit Product'),
actions: <Widget>[
IconButton(
icon: const Icon(Icons.save),
onPressed: _saveForm,
),
],
),
body: Padding(
padding: const EdgeInsets.all(16.0),
child: Form(
key: _form,
child: ListView(
children: <Widget>[
TextFormField(
initialValue: _initValues['title'],
decoration: const InputDecoration(labelText: 'Title'),
textInputAction: TextInputAction.next,
onFieldSubmitted: (_) {
FocusScope.of(context).requestFocus(_priceFocusNode);
},
validator: (value) {
if (value!.isEmpty) {
return 'Please provide a value.';
}
return null;
},
onSaved: (value) {
_editedProduct = Product(
title: value.toString(),
price: _editedProduct.price,
description: _editedProduct.description,
imageUrl: _editedProduct.imageUrl,
id: _editedProduct.id,
isFav: _editedProduct.isFav);
},
),
TextFormField(
initialValue: _initValues['price'],
decoration: const InputDecoration(labelText: 'Price'),
textInputAction: TextInputAction.next,
keyboardType: TextInputType.number,
focusNode: _priceFocusNode,
onFieldSubmitted: (_) {
FocusScope.of(context).requestFocus(_descriptionFocusNode);
},
validator: (value) {
if (value!.isEmpty) {
return 'Please enter a price.';
}
if (double.tryParse(value) == null) {
return 'Please enter a valid number.';
}
if (double.parse(value) <= 0) {
return 'Please enter a number greater than zero.';
}
return null;
},
onSaved: (value) {
_editedProduct = Product(
title: _editedProduct.title,
price: int.parse(value.toString()),
description: _editedProduct.description,
imageUrl: _editedProduct.imageUrl,
id: _editedProduct.id,
isFav: _editedProduct.isFav);
},
),
TextFormField(
initialValue: _initValues['description'],
decoration: const InputDecoration(labelText: 'Description'),
maxLines: 3,
keyboardType: TextInputType.multiline,
focusNode: _descriptionFocusNode,
validator: (value) {
if (value!.isEmpty) {
return 'Please enter a description.';
}
if (value.length < 10) {
return 'Should be at least 10 characters long.';
}
return null;
},
onSaved: (value) {
_editedProduct = Product(
title: _editedProduct.title,
price: _editedProduct.price,
description: value.toString(),
imageUrl: _editedProduct.imageUrl,
id: _editedProduct.id,
isFav: _editedProduct.isFav,
);
},
),
Row(
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
Container(
width: 100,
height: 100,
margin: const EdgeInsets.only(
top: 8,
right: 10,
),
decoration: BoxDecoration(
border: Border.all(
width: 1,
color: Colors.grey,
),
),
child: _imageUrlController.text.isEmpty
? const Text('Enter a URL')
: FittedBox(
child: Image.network(
_imageUrlController.text,
fit: BoxFit.cover,
),
),
),
Expanded(
child: TextFormField(
decoration: const InputDecoration(labelText: 'Image URL'),
keyboardType: TextInputType.url,
textInputAction: TextInputAction.done,
controller: _imageUrlController,
focusNode: _imageUrlFocusNode,
onFieldSubmitted: (_) {
_saveForm();
},
validator: (value) {
if (value!.isEmpty) {
return 'Please enter an image URL.';
}
if (!value.startsWith('http') &&
!value.startsWith('https')) {
return 'Please enter a valid URL.';
}
if (!value.endsWith('.png') &&
!value.endsWith('.jpg') &&
!value.endsWith('.jpeg')) {
return 'Please enter a valid image URL.';
}
return null;
},
onSaved: (value) {
_editedProduct = Product(
title: _editedProduct.title,
price: _editedProduct.price,
description: _editedProduct.description,
imageUrl: value.toString(),
id: _editedProduct.id,
isFav: _editedProduct.isFav,
);
},
),
),
],
),
],
),
),
),
);
}
}
这是我的产品类别
class Product with ChangeNotifier {
final String id;
final String title;
final String description;
final int price;
final String imageUrl;
bool isFav;
Product(
{required this.id,
required this.title,
required this.description,
required this.price,
required this.imageUrl,
this.isFav = false});
void toggleFavStatus() {
isFav = !isFav;
notifyListeners();
}
}
这是我的产品提供商类
class ProductsProvider with ChangeNotifier {
// ignore: prefer_final_fields
List<Product> _items = [
Product(
id: 'p1',
title: 'Red Shirt',
description: 'A red shirt - it is pretty red!',
price: 29,
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,
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,
imageUrl:
'https://live.staticflickr.com/4043/4438260868_cc79b3369d_z.jpg',
),
Product(
id: 'p4',
title: 'A Pan',
description: 'Prepare any meal you want.',
price: 49,
imageUrl:
'https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Cast-Iron-Pan.jpg/1024px-Cast-Iron-Pan.jpg',
),
];
List<Product> get items {
// if (_showFavoritesOnly) {
// return _items.where((prodItem) => prodItem.isFavorite).toList();
// }
return [..._items];
}
List<Product> get favoriteItems {
return _items.where((prodItem) => prodItem.isFav).toList();
}
Product findById(String id) {
return _items.firstWhere((prod) => prod.id == id);
}
void showFavoritesOnly() {
notifyListeners();
}
void showAll() {
notifyListeners();
}
void addProduct(Product product) {
final newProduct = Product(
title: product.title,
description: product.description,
price: product.price,
imageUrl: product.imageUrl,
id: DateTime.now().toString(),
);
_items.add(newProduct);
// _items.insert(0, newProduct); // at the start of the list
notifyListeners();
}
void updateProduct(String id, Product newProduct) {
final prodIndex = _items.indexWhere((prod) => prod.id == id);
if (prodIndex >= 0) {
_items[prodIndex] = newProduct;
notifyListeners();
} else {}
}
void deleteProduct(String id) {
_items.removeWhere((prod) => prod.id == id);
notifyListeners();
}
}
【问题讨论】：
-
你能包括你的产品和产品供应商吗
-
我刚刚添加了 请看一下
标签： flutter dart flutter-dependencies flutter-provider dart-null-safety