Dropdown button selection not update in Flutter

Question

I created my dropdown button, but whenever an item is selected does not update value.But whenever I hotreload all my values ​​are updated. Can anyone guess the reason? or is there a solution?

DropdownButton<String>(
                    value: dropdownValue,
                    icon: Icon(Icons.keyboard_arrow_down),
                    iconSize: 15,
                    elevation: 10,
                    style: TextStyle(color: Colors.grey),
                    onChanged: (newValue) {
                      setState(() async {
                        dropdownValue = newValue;
                    final selectedLanguage= await SharedPreferences.getInstance();
                    selectedLanguage.setString('selectedLanguage', dropdownValue);
                      });
                      allTranslations.setNewLanguage(
                        allTranslations.getLocaleKey(
                          dropdownValue,
                        ),
                      );
                    },
                    items: <String>[
                      englishText,
                      chineseText,
                      russianText,
                    ].map<DropdownMenuItem<String>>((String value) {
                      return DropdownMenuItem<String>(
                        value: value,
                        child: Text(value),
                      );
                    }).toList(),
                  ),

Answer 1

@kimSoo great that it worked!

Solution for everyone is the async closure in setstate wont work. We have to remove it and initialize Shared Preferences earlier.

Initialize final selectedLanguage= await SharedPreferences.getInstance(); earlier

DropdownButton<String>(
                    value: dropdownValue,
                    icon: Icon(Icons.keyboard_arrow_down),
                    iconSize: 15,
                    elevation: 10,
                    style: TextStyle(color: Colors.grey),
                    onChanged: (newValue) {
                      setState(() { <----- removed async
                        dropdownValue = newValue;
                    
                    selectedLanguage.setString('selectedLanguage', dropdownValue);
                      });
                      allTranslations.setNewLanguage(
                        allTranslations.getLocaleKey(
                          dropdownValue,
                        ),
                      );
                    },
                    items: <String>[
                      englishText,
                      chineseText,
                      russianText,
                    ].map<DropdownMenuItem<String>>((String value) {
                      return DropdownMenuItem<String>(
                        value: value,
                        child: Text(value),
                      );
                    }).toList(),
                  ),