input_page.dart

class InputPage extends StatelessWidget {
  ...
  Widget _buildCards(BuildContext context) {
    return Padding(
      padding: EdgeInsets.only(
        left: 14.0,
        right: 14.0,
        top: screenAwareSize(32.0, context),
      ),
      child: Row(
        children: <Widget>[
          Expanded(
            child: Column(
              children: <Widget>[
                Expanded(child: _tempCard("Gender")),
                Expanded(child: _tempCard("Weight")),
              ],
            ),
          ),
          Expanded(child: _tempCard("Height"))
        ],
      ),
    );
  }

  Widget _tempCard(String label) {
    return Card(
      child: Container(
        width: double.infinity,
        height: double.infinity,
        child: Text(label),
      ),
    );
  }
  ...
}