('InheritedWidget Example')), body: Center( child: Column( mainAxisAlignment: MainAxisAlignment.center, children: <Widget>[ Text('You have pushed the button this many times:'), Text('$_count'), // 使用 CountWidget 共享的数据 ], ), ), floatingActionButton: FloatingActionButton( ...
一、Widget的分类 二、有状态 Stateful Widget本质也是不可变的 三、Stateless Widget 无状态 3.1 什么是Stateless Widget? 3.2 生命周期和适用场景 3.3在日常开发中的典型使用 四、Stateful Widget 4.1 什么是State? 4.2 生命周期 4.3 获取State对象 4.4 如何创建Stateful Widget ...
title: Text('InheritedWidget Example'), ), body: Center( child: MyWidget(), ), ), ), ); } } void main() { runApp(MyApp()); } ``` 在上面的示例中,我们创建了一个名为 `MyData` 的自定义 InheritedWidget 子类,用于共享一个整数值。然后我们在 `MyApp` 中将 `MyData` 作为父节点,以便...
因为“页面”是以widget(组件)形式定义的,而页面里面的元素也是各种不同widget,例如html中的row、table以及css里面的padding都对应flutter中的某一个具体的widget。所以有人说,可以把flutter的页面构建过程理解成是“俄罗斯的套娃”,有不同的组件层层嵌套完成;也可以理解是一棵widget tree组件树,嵌套关系用“parent widg...
/// inherit from this widget but sometimes we do not. For example, if the data /// held by this widget is the same as the data held by `oldWidget`, then we /// do not need to rebuild the widgets that inherited the data held by ...
Widget build(BuildContext context) { return Scaffold( appBar: AppBar( title: const Text('Example'), ), body: Center( child: Column( mainAxisSize: MainAxisSize.min, mainAxisAlignment: MainAxisAlignment.center, children: const <Widget>[
子组件是通过 XXDataWidget.of(context).data 来获取数据的,为什么这里会需要传入一个 context 呢?因为 context 其实是 widget 所对应的 element,通过 of 方法,调用到子组件自己对应的 element 实例上的 getElementForInheritedWidgetOfExactType,通过该方法,取得实例上的祖先遗传节点(_inheritedWidgets)。如下源码所示...
When an inherited widget changes,forexampleifthevalueof Theme.of() changes, its dependent widgets are rebuilt. If the dependent widget's reference to the inherited widgetisina constructororaninitState() method, then the rebuilt dependent widget willnotreflect the changesinthe ...
inheritFromWidgetOfExactType(_InheritedTheme) or inheritFromElement() was called before initState() completed. When an inherited widget changes, for example if the value of Theme.of() changes, its dependent widgets are rebuilt. If the dependent widget's reference to the inherited widget is in ...
return context.dependOnInheritedWidgetOfExactType<CounterWidget>()!; } @override bool updateShouldNotify(InheritedWidget oldWidget) { return true; } } class CounterWidgetExample extends StatelessWidget { @override Widget build(BuildContext context) { ...