Counter app implemented with InheritedWidget

inherited_counter.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: MyHomePage(),
    );
  }
}

// Counter app with InheritedWidget

class MyHomePage extends StatelessWidget {
  Widget build(BuildContext context) {
    return CounterWidget(
      child: Scaffold(
        appBar: AppBar(
          title: Text("Page Title"),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Builder(builder: (context) {
                final inherited =
                    context.inheritFromWidgetOfExactType(_InheritedCount)
                        as _InheritedCount;
                return Text(
                  '${inherited.state.count}',
                  style: Theme.of(context).textTheme.display1,
                );
              }),
              Builder(builder: (context) {
                final ancestor =
                    context.ancestorWidgetOfExactType(_InheritedCount)
                        as _InheritedCount;
                return RaisedButton(
                  onPressed: () => ancestor.state.incrementCount(),
                  child: Text("Increment"),
                );
              }),
            ],
          ),
        ),
      ),
    );
  }
}

class CounterWidget extends StatefulWidget {
  CounterWidget({Key key, @required this.child}) : super(key: key);

  final Widget child;

  @override
  _CounterState createState() => _CounterState();
}

class _CounterState extends State<CounterWidget> {
  int count;

  void incrementCount() {
    setState(() {
      ++count;
    });
  }

  @override
  void initState() {
    super.initState();
    count = 0;
  }

  @override
  Widget build(BuildContext context) {
    return _InheritedCount(
      state: this,
      child: widget.child,
    );
  }
}

class _InheritedCount extends InheritedWidget {
  _InheritedCount({Key key, @required this.state, @required Widget child})
      : super(key: key, child: child);

  final _CounterState state;

  @override
  bool updateShouldNotify(_InheritedCount old) => true;
}