flutter_friday_8_3.dart

class MyApp extends StatelessWidget {
  Stream<int> _countUp() async* {
    for (int i = 1; i <= 10; i++) {
      yield await Future.delayed(Duration(seconds: 1), () => i);
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Counting with Streams',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Let\'s count!'),
        ),
        body: Center(
          child: StreamBuilder<int>(
            stream: _countUp(),
            builder: (context, snapshot) => Text(
                snapshot?.data?.toString() ?? '0',
                style: Theme.of(context).textTheme.headline),
          ),
        ),
      ),
    );
  }
}