当ShoppingList小部件首次插入到树中时,框架将调用createState函数来创建_ShoppingListState的新实例,以便与该树中的该位置关联。(请注意,我们通常使用前导下划线来命名State的子类,以指示它们是私有实现细节。)当此小部件的父级重建时,父级将创建ShoppingList的新实例,但该框架将重新使用树已存在的_ShoppingListState实...
当ShoppingList首次插入到Widget树中时,框架会调用其createState函数以创建一个新的_ShoppingListState实例来与该Widget树中的相应位置关联(请注意,我们通常命名State子类时带一个下划线,这表示其是私有的)。 当这个Widget的父级Widget重建时,父级Widget将创建一个新的ShoppingList实例,Flutter框架将重用已经在Widget树中...
I'm a beginner of Flutter. I'm making a sort of shopping list app. Using this tutorial https://www.youtube.com/watch?v=ZnevdXDH25Q I'm trying to use GetX for state management. I have this class named 'Items' which has some attributes. I create a list of Items...
//_shoppingCart inside a setState call to trigger a rebuild. // The framework then calls // build, below, // which updates the visual appearance of the app. if (!inCart) _shoppingCart.add(product); else _shoppingCart.remove(product); }); } @override Widget build(BuildContext context)...
Moreover, we'll have to use navigation features as well. We'll also need a person icon somewhere in the app bar, which we'll trigger the custom drawer we'll create later. Maybe we'll want to add icons like shopping cart, bell icon, and more depending on the page, we are on....
让我们考虑一个更完整的示例,它将上面介绍的概念结合在一起。让我们假设一个显示各种待售产品并维护购物车的购物应用程序。让我们先定义ShoppingListItem: class Product { const Product({this.name}); final String name; } typedef void CartChangedCallback(Product product, bool inCart); ...
// build, below, which updates the visual appearance of the app. if (inCart) _shoppingCart.add(product); else _shoppingCart.remove(product); }); } @override Widget build(BuildContext context) { return new Scaffold( appBar: new AppBar( ...
voidmain(){runApp(constMaterialApp(title:"Shopping App",home:ShoppingList(products:[Product(name:"Eggs"),Product(name:"Flour"),Product(name:"Chocolate chips"),]),));//runApp(const MaterialApp(home: Scaffold(body: Center(child: Counter2()));//runApp(const MaterialApp(home: Scaffold(body:...
例如,ShoppingList构建了足够的ShoppingListItem实例来填充其可见区域: 如果没有密钥,则当前生成中的第一个项将始终与上一个生成中的首个项同步。即使在语义上,如果列表中的第一个项目滚动到屏幕外,它在窗口中也不再可见。 通过将列表中的每个项目指定为“语义”键,无限列表可以更有效,因为框架将使项目与匹配的...
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