main3 Dart File

main3.dart

Widget build(BuildContext context) {
  List<Widget> remaining = widget.items.sublist(_done);
  return new Scaffold(
    body: (remaining.length <= 3)
        ? new Column(children: remaining)
        : new Text('${remaining.length} items left to do'),
    floatingActionButton: new FloatingActionButton(onPressed: _doOneThing),
  );
}