gender_card.dart

double _circleSize(BuildContext context) => screenAwareSize(80.0, context);

class _GenderCardState extends State<GenderCard> {
  @override
  Widget build(BuildContext context) {
    return ...
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            children: <Widget>[
              CardTitle("GENDER"),
              Padding(
                padding: EdgeInsets.only(top: screenAwareSize(16.0, context)),
                child: _drawMainStack(),
              ),
            ],
          ),
        ...
  }

  Widget _drawMainStack() {
    return Stack(
      alignment: Alignment.bottomCenter,
      children: <Widget>[
        _drawCircleIndicator(),
      ],
    );
  }

  Widget _drawCircleIndicator() {
    return Stack(
      alignment: Alignment.center,
      children: <Widget>[
        GenderCircle(),
      ],
    );
  }

}


class GenderCircle extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      width: _circleSize(context),
      height: _circleSize(context),
      decoration: BoxDecoration(
        shape: BoxShape.circle,
        color: Color.fromRGBO(244, 244, 244, 1.0),
      ),
    );
  }
}