example of dropdownbutton in flutter

dropdown_example.dart

DropdownButton(
                iconSize: 45.0,
                  items: <String>[
                          'MTN',
                         'TIGO',
                          'AIRTEL'].map((String value) {
                        return DropdownMenuItem<String>(
                               value: value,
                         child: Text(value),
                        );
                        }).toList(),
                        onChanged: (String value) {
                           isSelected = value;
                      });