Flutter InheritedWidget test

inherited_widget_test.dart

import 'dart:math';

import 'package:flutter/material.dart';
import 'package:meta/meta.dart';

void main() {
  runApp(new AppContainer());
}

class AppContextData {
  final String appName;
  final int value;
  final ThemeData themeData;

  const AppContextData({this.appName, this.value, this.themeData});

  AppContextData withName(String newAppName) {
    return new AppContextData(
        appName: newAppName, value: value, themeData: themeData);
  }

  AppContextData increment() {
    return new AppContextData(
        appName: appName, value: value + 1, themeData: themeData);
  }

  AppContextData withTheme(ThemeData themeData) {
    return new AppContextData(
        appName: appName, value: value, themeData: themeData);
  }
}

class AppContext extends InheritedWidget {
  final AppContextData appContextData;
  final Function(String title) updateTitle;
  final Function() increment;
  final Function() changeTheme;

  AppContext({
    Key key,
    @required this.appContextData,
    @required this.updateTitle,
    @required this.increment,
    @required this.changeTheme,
    @required Widget child,
  })
      : super(key: key, child: child);

  static AppContext of(BuildContext context) {
    return context.inheritFromWidgetOfExactType(AppContext);
  }

  @override
  bool updateShouldNotify(AppContext old) =>
      appContextData != old.appContextData;
}

class AppContainer extends StatefulWidget {
  @override
  _AppContainerState createState() => new _AppContainerState();
}

class _AppContainerState extends State<AppContainer> {
  AppContextData appContextData;

  @override
  void initState() {
    appContextData = new AppContextData(
        appName: "mon titre",
        value: 0,
        themeData: new ThemeData(
          primarySwatch: Colors.blue,
        ));

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return new AppContext(
        appContextData: appContextData,
        updateTitle: _updateTitle,
        increment: _increment,
        changeTheme: _changeTheme,
        child: new MyApp());
  }

  void _updateTitle(String title) {
    setState(() {
      appContextData = appContextData.withName(title);
    });
  }

  void _increment() {
    setState(() {
      appContextData = appContextData.increment();
    });
  }

  void _changeTheme() {
    setState(() {
      Random rnd = new Random();
      var index = rnd.nextInt(Colors.primaries.length);
      appContextData = appContextData.withTheme(new ThemeData(
        primarySwatch: Colors.primaries[index],
      ));
    });
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final appContext = AppContext.of(context);
    final appContextData = appContext.appContextData;

    return new MaterialApp(
      title: 'Flutter Demo',
      theme: appContextData.themeData,
      home: new MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final appContext = AppContext.of(context);
    final appContextData = appContext.appContextData;

    return new Scaffold(
      appBar: new AppBar(
        title: new Text(appContextData.appName),
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new Text(
              'You have pushed the button this many times:',
            ),
            new Text(
              '${appContextData.value}',
              style: Theme.of(context).textTheme.display1,
            ),
            new Text("Set new title below:"),
            new TextField(onChanged: appContext.updateTitle),
            new RaisedButton(
              onPressed: appContext.changeTheme,
              child: new Text("change theme"),
            )
          ],
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: appContext.increment,
        tooltip: 'Increment',
        child: new Icon(Icons.add),
      ),
    );
  }
}