徐州市建设局网站,软件工程考研要考哪些科目,网站建设的开源平台,天猫与京东的网站建设管理文章目录 1.flutter widget分类2. 代理组件又分为3. 状态 state 数据4. 刷新 数据变化5. code 1.flutter widget分类 组合渲染代理 2. 代理组件又分为 Positioned向父组件传递数据InheritedWidget向子组件传递数据 3. 状态 state 数据 状态就是用到了向子组件传递数据#xff… 文章目录 1.flutter widget分类2. 代理组件又分为3. 状态 state 数据4. 刷新 数据变化5. code 1.flutter widget分类 组合渲染代理 2. 代理组件又分为 Positioned向父组件传递数据InheritedWidget向子组件传递数据 3. 状态 state 数据 状态就是用到了向子组件传递数据并且需要刷新的时候刷新组件 4. 刷新 数据变化 获取并在改变的时候会导致刷新 dependOnInheritedWidgetOfExactType只获取不会因为数据变化导致刷新 getInheritedWidgetOfExactType 5. code
import package:flutter/material.dart;//material cupertino
//widget
//rendering
//foundation 动画 事件 painting
//flutter框架层
//engine
//embedded嵌入式main() {runApp(const MaterialApp(home: StateStudyPage(),));
}class StateStudyPage extends StatefulWidget {const StateStudyPage({super.key});overrideStateStateStudyPage createState() _StateStudyPageState();
}class _StateStudyPageState extends StateStateStudyPage {int aa 0;int dt1 0;int dt2 0;overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(),body: ShareData2Widget(dt1: dt1,dt2: dt2,child: Column(children: [Text(parent$aa),TextButton(onPressed: () {setState(() {aa;});},child: Text(刷新当前state)),TextButton(onPressed: () {setState(() {dt1;});},child: Text(刷新当前state dt1$dt1)),TextButton(onPressed: () {setState(() {dt2;});},child: Text(刷新当前state dt2$dt2)),StateStudyChildPage(aa: aa,),],),),);}
}class StateStudyChildPage extends StatefulWidget {final int aa;const StateStudyChildPage({super.key, required this.aa});overrideStateStateStudyChildPage createState() _StateStudyChildPageState();
}class _StateStudyChildPageState extends StateStateStudyChildPage {int a 0;///由于父widget setState 导致该方法调用overridevoid didUpdateWidget(covariant StateStudyChildPage oldWidget) {super.didUpdateWidget(oldWidget);print(更新widget);}///由于用到了共享数据并在数据变化的时候调用了父组件的setState导致该方法调用overridevoid didChangeDependencies() {super.didChangeDependencies();print(依赖变化);}overrideWidget build(BuildContext context) {return Column(children: [Text(child$a),Text(childaa${widget.aa}),Text(childcc${ShareData2Widget.of(context, data)?.dt1}),TextButton(onPressed: () {setState(() {a;});},child: Text(刷新当前state))],);}
}///整体数据刷新
class ShareDataWidget extends InheritedWidget {const ShareDataWidget({super.key,required this.data,required super.child,});final int data; //需要在子树中共享的数据保存点击次数//定义一个便捷方法方便子树中的widget获取共享数据static ShareDataWidget? of(BuildContext context) {return context.dependOnInheritedWidgetOfExactTypeShareDataWidget();}//该回调决定当data发生变化时是否通知子树中依赖data的Widget重新buildoverridebool updateShouldNotify(ShareDataWidget oldWidget) {return oldWidget.data ! data;}
}///局部数据导致刷新
class ShareData2Widget extends InheritedModelString {const ShareData2Widget({super.key,required this.dt2,required this.dt1,required super.child,});final int dt1;final int dt2;//定义一个便捷方法方便子树中的widget获取共享数据//type就是根据type来判断是否需要刷新组件static ShareData2Widget? of(BuildContext context, String type) {return context.dependOnInheritedWidgetOfExactTypeShareData2Widget(aspect: type);}//该回调决定当data发生变化时是否通知子树中依赖data的Widget重新buildoverridebool updateShouldNotify(ShareData2Widget oldWidget) {print(oldWidget.dt1 ! dt1${oldWidget.dt1 ! dt1});return oldWidget.dt1 ! dt1 || oldWidget.dt2 ! dt2;}overridebool updateShouldNotifyDependent(covariant ShareData2Widget oldWidget, SetString dependencies) {return dependencies.contains(data) oldWidget.dt1 ! dt1 ||dependencies.contains(data2) oldWidget.dt2 ! dt2;}
}
