Flutter-multi-level-dropdown-09.dart

Container(
          padding: EdgeInsets.symmetric(horizontal: 50, vertical: 30),
          child: Column(
            children: <Widget>[
              DropdownButton<String>(
                isExpanded: true,
                items: _states.map((String dropDownStringItem) {
                  return DropdownMenuItem<String>(
                    value: dropDownStringItem,
                    child: Text(dropDownStringItem),
                  );
                }).toList(),
                onChanged: (value) => _onSelectedState(value),
                value: _selectedState,
              ),
              DropdownButton<String>(
                isExpanded: true,
                items: _lgas.map((String dropDownStringItem) {
                  return DropdownMenuItem<String>(
                    value: dropDownStringItem,
                    child: Text(dropDownStringItem),
                  );
                }).toList(),
                // onChanged: (value) => print(value),
                onChanged: (value) => _onSelectedLGA(value),
                value: _selectedLGA,
              ),
            ],
          ),
        )