文章目录
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- [1.flutter widget分类](#1.flutter widget分类)
- [2. 代理组件又分为](#2. 代理组件又分为)
- [3. 状态 state 数据](#3. 状态 state 数据)
- [4. 刷新 数据变化](#4. 刷新 数据变化)
- [5. code](#5. code)
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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
dart
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});
@override
State<StateStudyPage> createState() => _StateStudyPageState();
}
class _StateStudyPageState extends State<StateStudyPage> {
int aa = 0;
int dt1 = 0;
int dt2 = 0;
@override
Widget 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=$dt2")),
StateStudyChildPage(
aa: aa,
),
],
),
),
);
}
}
class StateStudyChildPage extends StatefulWidget {
final int aa;
const StateStudyChildPage({super.key, required this.aa});
@override
State<StateStudyChildPage> createState() => _StateStudyChildPageState();
}
class _StateStudyChildPageState extends State<StateStudyChildPage> {
int a = 0;
///由于父widget setState 导致该方法调用
@override
void didUpdateWidget(covariant StateStudyChildPage oldWidget) {
super.didUpdateWidget(oldWidget);
print("更新widget");
}
///由于用到了共享数据,并在数据变化的时候调用了父组件的setState,导致该方法调用
@override
void didChangeDependencies() {
super.didChangeDependencies();
print("依赖变化");
}
@override
Widget build(BuildContext context) {
return Column(
children: [
Text("child=$a"),
Text("child==aa=${widget.aa}"),
Text("child==cc=${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.dependOnInheritedWidgetOfExactType<ShareDataWidget>();
}
//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build
@override
bool updateShouldNotify(ShareDataWidget oldWidget) {
return oldWidget.data != data;
}
}
///局部数据导致刷新
class ShareData2Widget extends InheritedModel<String> {
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.dependOnInheritedWidgetOfExactType<ShareData2Widget>(
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build
@override
bool updateShouldNotify(ShareData2Widget oldWidget) {
print("oldWidget.dt1 != dt1=${oldWidget.dt1 != dt1}");
return oldWidget.dt1 != dt1 || oldWidget.dt2 != dt2;
}
@override
bool updateShouldNotifyDependent(
covariant ShareData2Widget oldWidget, Set<String> dependencies) {
return dependencies.contains("data") && oldWidget.dt1 != dt1 ||
dependencies.contains("data2") && oldWidget.dt2 != dt2;
}
}