values.dart

class MyHomePage extends StatelessWidget {
  final _counter = new ValueNotifier(0);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("ValueListenableBuilder example"),
        ),
        body: CounterListenableProvider(
          counter: _counter,
          child: Center(
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text('You have pushed the button this many times:'),
                CounterText()
              ],
            ),
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: () => _counter.value++,
          tooltip: 'Increment',
          child: Icon(Icons.add),
        ));
  }
}