资料
例子
import 'package:flutter/material.dart';
class InheritedTestModel {
final int count;
const InheritedTestModel(this.count);
}
class InheritedContext extends InheritedWidget {
// 数据
final InheritedTestModel inheritedTestModel;
// 点击+号的方法
final Function() increment;
// 点击-号的方法
final Function() reduce;
InheritedContext({
Key? key,
required this.inheritedTestModel,
required this.increment,
required this.reduce,
required Widget child,
}) : super(key: key, child: child);
static InheritedContext? of(BuildContext context, {bool rebuild = true}) {
// if (rebuild) {
return context.dependOnInheritedWidgetOfExactType<InheritedContext>();
// } else {
// return context.getElementForInheritedWidgetOfExactType<InheritedContext>();
// }
}
@override
bool updateShouldNotify(covariant InheritedContext oldWidget) {
return inheritedTestModel != oldWidget.inheritedTestModel;
}
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: "Welcome to Flutter",
home: Scaffold(
appBar: AppBar(title: Text('Hello')),
body: InheritedWidgetTestContainer(),
),
);
}
}
class TestWidgetA extends StatelessWidget {
@override
Widget build(BuildContext context) {
final inheritedContext = InheritedContext.of(context);
final inheritedTestModel = inheritedContext?.inheritedTestModel;
print('TestWidgetA 中的count的值：${inheritedTestModel?.count}');
return Padding(
padding: EdgeInsets.only(left: 10.0, top: 10.0, right: 10.0),
child: RaisedButton(
onPressed: inheritedContext?.increment,
textColor: Colors.black,
child: new Text('+'),
),
);
}
}
class TestWidgetB extends StatelessWidget {
@override
Widget build(BuildContext context) {
final inheritedContext = InheritedContext.of(context);
final inheritedTestModel = inheritedContext?.inheritedTestModel;
print('TestWidgetB 中count的值:${inheritedTestModel?.count}');
return Padding(
padding: EdgeInsets.only(left: 10.0, top: 10.0, right: 10.0),
child: Text(
'当前count:${inheritedTestModel?.count}',
style: TextStyle(fontSize: 20.0),
),
);
}
}
class TestWidgetC extends StatelessWidget {
@override
Widget build(BuildContext context) {
final inheritedContext = InheritedContext.of(context);
final inheritedTestModel = inheritedContext?.inheritedTestModel;
print('TestWidgetC 中count的值：${inheritedTestModel?.count}');
return Padding(
padding: EdgeInsets.only(left: 10.0, top: 10.0, right: 10.0),
child: RaisedButton(
textColor: Colors.black,
child: Text('-'),
onPressed: inheritedContext?.reduce,
),
);
}
}
class InheritedWidgetTestContainer extends StatefulWidget {
@override
State<StatefulWidget> createState() => _InheritedWidgetTestContainerState();
}
class _InheritedWidgetTestContainerState
extends State<InheritedWidgetTestContainer> {
late InheritedTestModel inheritedTestModel;
@override
void initState() {
inheritedTestModel = InheritedTestModel(0);
super.initState();
}
_incrementCount() {
setState(() {
inheritedTestModel = InheritedTestModel(inheritedTestModel.count + 1);
});
}
_reduceCount() {
setState(() {
inheritedTestModel = InheritedTestModel(inheritedTestModel.count - 1);
});
}
@override
Widget build(BuildContext context) {
return InheritedContext(
inheritedTestModel: inheritedTestModel,
increment: _incrementCount,
reduce: _reduceCount,
child: Scaffold(
appBar: AppBar(title: Text('InheritedWidgetTest')),
body: Column(
children: [
Padding(
padding: EdgeInsets.only(left: 10.0, top: 10.0, right: 10.0),
child: Text(
'我们常使用的\nTheme.of(context).textTheme\nMediaQuery.of'
'(context).size等\n就是通过InheritedWidget实现的',
style: TextStyle(fontSize: 20.0),
),
),
TestWidgetA(),
TestWidgetB(),
TestWidgetC(),
],
),
),
);
}
}1. 先创建一个继承InheritedWidget的子类InheritedContext
class InheritedContext extends InheritedWidget {
// 数据
final InheritedTestModel inheritedTestModel;
// 点击+号的方法
final Function() increment;
// 点击-号的方法
final Function() reduce;
InheritedContext({
Key? key,
required this.inheritedTestModel,
required this.increment,
required this.reduce,
required Widget child,
}) : super(key: key, child: child);
static InheritedContext? of(BuildContext context, {bool rebuild = true}) {
// if (rebuild) {
return context.dependOnInheritedWidgetOfExactType<InheritedContext>();
// } else {
// return context.getElementForInheritedWidgetOfExactType<InheritedContext>();
// }
}
@override
bool updateShouldNotify(covariant InheritedContext oldWidget) {
return inheritedTestModel != oldWidget.inheritedTestModel;
}
}这个类作为你要parent widget存在。
通过以下来创建以来
static InheritedContext? of(BuildContext context, {bool rebuild = true}) {
// if (rebuild) {
return context.dependOnInheritedWidgetOfExactType<InheritedContext>();
// } else {
// return context.getElementForInheritedWidgetOfExactType<InheritedContext>();
// }
}设置监听(TestWIdgetA、TestWidgetB、TestWidgetC)
final inheritedContext = InheritedContext.of(context);
final inheritedTestModel = inheritedContext?.inheritedTestModel;从widget树中遍历，得到有效的数据。
实例2
import 'package:flutter/material.dart';
class InheritedTestModel {
final int count;
const InheritedTestModel(this.count);
}
class InheritedContext extends InheritedWidget {
// 数据
final InheritedTestModel inheritedTestModel;
// 点击+号的方法
final Function() increment;
// 点击-号的方法
final Function() reduce;
InheritedContext({
Key? key,
required this.inheritedTestModel,
required this.increment,
required this.reduce,
required Widget child,
}) : super(key: key, child: child);
static InheritedContext? of(BuildContext context, {bool rebuild = true}) {
if (rebuild) {
return context.dependOnInheritedWidgetOfExactType<InheritedContext>();
} else {
final w = context
.getElementForInheritedWidgetOfExactType<InheritedContext>()
?.widget;
if (w is InheritedContext) {
return w;
} else {
return context.dependOnInheritedWidgetOfExactType<InheritedContext>();
}
}
}
@override
bool updateShouldNotify(covariant InheritedContext oldWidget) {
return inheritedTestModel != oldWidget.inheritedTestModel;
}
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: "Welcome to Flutter",
home: Scaffold(
appBar: AppBar(title: Text('Hello')),
body: InheritedWidgetTestContainer(),
),
);
}
}
class TestWidgetA extends StatelessWidget {
@override
Widget build(BuildContext context) {
// 去InheritedContext里面取值,重新构建的时候
final inheritedContext = InheritedContext.of(context);
final inheritedTestModel = inheritedContext?.inheritedTestModel;
print('TestWidgetA 中的count的值：${inheritedTestModel?.count}');
return Padding(
padding: EdgeInsets.only(left: 10.0, top: 10.0, right: 10.0),
child: RaisedButton(
onPressed: inheritedContext?.increment,
textColor: Colors.black,
child: new Text('+'),
),
);
}
}
class TestWidgetB extends StatelessWidget {
@override
Widget build(BuildContext context) {
final inheritedContext = InheritedContext.of(context);
final inheritedTestModel = inheritedContext?.inheritedTestModel;
print('TestWidgetB 中count的值:${inheritedTestModel?.count}');
return Padding(
padding: EdgeInsets.only(left: 10.0, top: 10.0, right: 10.0),
child: Text(
'当前count:${inheritedTestModel?.count}',
style: TextStyle(fontSize: 20.0),
),
);
}
}
class TestWidgetC extends StatelessWidget {
@override
Widget build(BuildContext context) {
final inheritedContext = InheritedContext.of(context);
final inheritedTestModel = inheritedContext?.inheritedTestModel;
print('TestWidgetC 中count的值：${inheritedTestModel?.count}');
return Padding(
padding: EdgeInsets.only(left: 10.0, top: 10.0, right: 10.0),
child: RaisedButton(
textColor: Colors.black,
child: Text('-'),
onPressed: inheritedContext?.reduce,
),
);
}
}
class InheritedWidgetTestContainer extends StatefulWidget {
@override
State<StatefulWidget> createState() => _InheritedWidgetTestContainerState();
}
class _InheritedWidgetTestContainerState
extends State<InheritedWidgetTestContainer> {
late InheritedTestModel inheritedTestModel;
@override
void initState() {
inheritedTestModel = InheritedTestModel(0);
super.initState();
}
_incrementCount() {
setState(() {
inheritedTestModel = InheritedTestModel(inheritedTestModel.count + 1);
});
}
_reduceCount() {
setState(() {
inheritedTestModel = InheritedTestModel(inheritedTestModel.count - 1);
});
}
@override
Widget build(BuildContext context) {
print('_InheritedWidgetTestContainerState build(BuildContext...');
return InheritedContext(
inheritedTestModel: inheritedTestModel,
increment: _incrementCount,
reduce: _reduceCount,
child: Scaffold(
appBar: AppBar(title: Text('InheritedWidgetTest')),
body: Column(
children: [
Padding(
padding: EdgeInsets.only(left: 10.0, top: 10.0, right: 10.0),
child: Text(
'我们常使用的\nTheme.of(context).textTheme\nMediaQuery.of'
'(context).size等\n就是通过InheritedWidget实现的',
style: TextStyle(fontSize: 20.0),
),
),
TestWidgetA(),
TestWidgetB(),
TestWidgetC(),
],
),
),
);
}
}
