finish inherited

lib/config/RouterConfig.dart

@@ -8,6 +8,7 @@ import 'package:flutter_starter_notes/ui/FlexAbout.dart';
 import 'package:flutter_starter_notes/ui/GridViewAbout.dart';
 import 'package:flutter_starter_notes/ui/HomePage.dart';
 import 'package:flutter_starter_notes/ui/ImageAndIconAbout.dart';
+import 'package:flutter_starter_notes/ui/InheritedWidgetAbout.dart';
 import 'package:flutter_starter_notes/ui/InputAndFormAbout.dart';
 import 'package:flutter_starter_notes/ui/ListViewAbout.dart';
 import 'package:flutter_starter_notes/ui/MaterialContainerAbout.dart';
@@ -206,6 +207,14 @@ class RouterConfig {
             title: "导航返回拦截-WillPopScope",
           ),
     ),
+    RouterBean(
+      "/inheritedwidgetabout",
+      "数据共享-InheritedWidget",
+      "function",
+      (context) => InheritedWidgetAbout(
+            title: "数据共享-InheritedWidget",
+          ),
+    ),
   ];
 
   static Map<String, WidgetBuilder> genRouters() {

lib/ui/InheritedWidgetAbout.dart

@@ -0,0 +1,109 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_starter_notes/component/CommonTitle.dart';
+
+class InheritedWidgetAbout extends StatelessWidget {
+  InheritedWidgetAbout({Key key, this.title});
+
+  final String title;
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(title),
+      ),
+      body: SingleChildScrollView(
+        child: Column(
+          children: <Widget>[
+            CommonTitle('InheritedWidget 介绍与示例'),
+            Container(
+              padding: EdgeInsets.all(16),
+              child: Text(
+                  "InheritedWidget是Flutter中非常重要的一个功能型Widget，它可以高效的将数据在Widget树中向下传递、共享，这在一些需要在Widget树中共享数据的场景中非常方便，如Flutter中，正是通过InheritedWidget来共享应用主题(Theme)和Locale(当前语言环境)信息的。"),
+            ),
+            Container(
+              padding: EdgeInsets.fromLTRB(16, 0, 16, 16),
+              child: Text(
+                  "1. heritedWidget和React中的context功能类似，和逐级传递数据相比，它们能实现组件跨级传递数据。\n2. InheritedWidget的在Widget树中数据传递方向是从上到下的，这和Notification的传递方向正好相反"),
+            ),
+            InheritedWidgetTestRoute()
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+class ShareDataWidget extends InheritedWidget {
+  ShareDataWidget({@required this.data, Widget child}) : super(child: 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.inheritFromWidgetOfExactType(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
+  @override
+  bool updateShouldNotify(ShareDataWidget old) {
+    //如果返回true，则子树中依赖(build函数中有调用)本widget
+    //的子widget的`state.didChangeDependencies`会被调用
+    return old.data != data;
+  }
+}
+
+class _TestWidget extends StatefulWidget {
+  @override
+  __TestWidgetState createState() => new __TestWidgetState();
+}
+
+class __TestWidgetState extends State<_TestWidget> {
+  @override
+  Widget build(BuildContext context) {
+    //使用InheritedWidget中的共享数据
+    return Text(ShareDataWidget.of(context).data.toString());
+  }
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    //父或祖先widget中的InheritedWidget改变(updateShouldNotify返回true)时会被调用。
+    //如果build中没有依赖InheritedWidget，则此回调不会被调用。
+    print("Dependencies change");
+  }
+}
+
+class InheritedWidgetTestRoute extends StatefulWidget {
+  @override
+  _InheritedWidgetTestRouteState createState() =>
+      new _InheritedWidgetTestRouteState();
+}
+
+class _InheritedWidgetTestRouteState extends State<InheritedWidgetTestRoute> {
+  int count = 0;
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      child: ShareDataWidget(
+        //使用ShareDataWidget
+        data: count,
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: <Widget>[
+            Padding(
+              padding: const EdgeInsets.only(bottom: 20.0),
+              child: _TestWidget(), //子widget中依赖ShareDataWidget
+            ),
+            RaisedButton(
+              child: Text("Increment"),
+              //每点击一次，将count自增，然后重新build,ShareDataWidget的data将被更新
+              onPressed: () => setState(() => ++count),
+            )
+          ],
+        ),
+      ),
+    );
+  }
+}