How to update state of a ModalBottomSheet in Flutter?

Question

This code is very simple: shows a modal bottom sheet and when the uses clicks the button, it increases the height of the sheet by 10.

But nothing happens. Actually,

Answer 1

Screenshot:

---

Create a class:

class MyBottomSheet extends StatefulWidget {
  @override
  _MyBottomSheetState createState() => _MyBottomSheetState();
}

class _MyBottomSheetState extends State {
  bool _flag = false;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        FlutterLogo(
          size: 300,
          style: FlutterLogoStyle.stacked,
          textColor: _flag ? Colors.black : Colors.red,
        ),
        RaisedButton(
          onPressed: () => setState(() => _flag = !_flag),
          child: Text('Change Color'),
        )
      ],
    );
  }
}

Usage:

showModalBottomSheet(
  context: context,
  builder: (_) => MyBottomSheet(),
);