step3.dart

  @override
  Widget build(BuildContext context) {
    return new Container(
        color: Colors.white,
        child: new Center(
            child:
            new DropdownButton(
              value: _currentCity,
              items: _dropDownMenuItems,
              onChanged: changedDropDownItem,
            )
        )
    );
  }

  void changedDropDownItem(String selectedCity) {
    print("Selected city $selectedCity, we are going to refresh the UI");
    setState(() {
      _currentCity = selectedCity;
    });
  }