values.dart

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