layoutbuilder

layoutbuilder.dart

@override
  Widget build(BuildContext context) {
    return LayoutBuilder(
      builder: activityContainer,
    );
  }  

Widget activityContainer(BuildContext context, BoxConstraints constraint) {
    final ThemeData _theme = Theme.of(context);
    return Container(
      child: Stack(
        children: <Widget>[
          _backView(_theme),
         _frontView()],
      ),
    );
  }