Simplest InheritedWidget with State Update Example

main.dart

import 'dart:async';

import 'package:flutter/material.dart';

void main() {
  runApp(CounterUpdater(
    child: MyApp(),
  ));
}

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

  final Widget child;

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

class _CounterUpdaterState extends State<CounterUpdater> {
  int count = 42;
  @override
  void initState() {
    super.initState();
    Timer.periodic(Duration(seconds: 1), (timer) {
      setState(() {
        count++;
      });
    });
  }
  @override
  Widget build(BuildContext context) {
    return CountProvider(
      count: count,
      child: widget.child,
    );
  }
}

class CountProvider extends InheritedWidget {
  final Widget child;
  final int count;

  CountProvider({Key key, this.child, this.count}) : super(key: key, child: child);

  static CountProvider of(BuildContext context) => context.dependOnInheritedWidgetOfExactType(aspect: CountProvider);

  @override
  bool updateShouldNotify(CountProvider oldWidget) => true;
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: RichText(
        text: TextSpan(text: CountProvider.of(context).count.toString()),
        textDirection: TextDirection.ltr,
      ),
    );
  }
}