Flutter DropdownButton show label when option is selected

Change DropdownButton to DropdownButtonFormField and add this decoration....

              decoration: InputDecoration(
                filled: true,
                fillColor: Hexcolor('#ecedec'),
                labelText: 'Occupation',
                border: new CustomBorderTextFieldSkin().getSkin(),
              ),

Replace DropdownButton with DropdownButtonFormField:

https://api.flutter.dev/flutter/material/DropdownButtonFormField-class.html