DropdownButton(
  items: LanguageUtils.getSupportedLanguagesAsStringList()
      .map<DropdownMenuItem<String>>((String langCodeString) {
    return DropdownMenuItem<String>(
      value: langCodeString,
      child: buildLanguageRowForDropDownButton(
          langCode:
              LanguageUtils.getLangCodeFromItsStringRep(langCodeString)),
    );
  }).toList(),
  value: LanguageUtils.getStringRepForLangCode(_chosenLangCode),
  onChanged: (String? value) {
    changeLanguage();
  },
);
/// Build row to be displayed in DropDownMenu.
Row buildLanguageRowForDropDownButton({LangCode? langCode}) {
  // Use currently _chosenLangCode as default.
  langCode = langCode ?? _chosenLangCode;
  // Build row from settings.
  List<Widget> rowElements = [];
  if (showFlag) {
    rowElements.add(getImageOfLangCode(langCode: langCode));
  }
  if (showWrittenLanguage) {
    rowElements
        .add(Text(LanguageUtils.getFullNameForLangCode(langCode)));
  }
  return Row(
    mainAxisAlignment: MainAxisAlignment.spaceEvenly,
    children: rowElements,
  );
}

// LanguageUtils
/// Functions around setting app translation language.
class LanguageUtils {
  LanguageUtils() {}
  /// Get written rep of language to display to user.
  static String getFullNameForLangCode(LangCode langCodeToGetStringFor) {
    switch (langCodeToGetStringFor) {
      case LangCode.en:
        return "English";
        break;
      case LangCode.de:
        return "Deutsch";
        break;
    }
  }
  /// Get short rep of language code to use programmatically when exporting state.
  static String getStringRepForLangCode(LangCode langCodeToGetStringFor) {
    switch (langCodeToGetStringFor) {
      case LangCode.en:
        return "en";
        break;
      case LangCode.de:
        return "de";
        break;
    }
  }
  /// Get all supported LangCodes as string rep to create dropdown menu from.
  static List<String> getSupportedLanguagesAsStringList() {
    return LangCode.values.map((e) => e.name).toList();
  }
  /// To return LangCode from its converted rep.
  ///
  /// Defaults to en => Failsafe, always returns valid LangCode.
  static LangCode getLangCodeFromItsStringRep(String langCodeAsString) {
    switch (langCodeAsString) {
      case "de":
        return LangCode.de;
        break;
      case "en":
      default:
        return LangCode.en;
        break;
    }
  }
}
/// Supported Languages.
enum LangCode { en, de }

import 'package:flutter/material.dart';
const List<String> list = <String>['One  ', 'Two ', 'Three', 'Four'];
void main() => runApp(const DropdownButtonApp());
class DropdownButtonApp extends StatelessWidget {
const DropdownButtonApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: const Text('DropdownButton Sample')),
body: const Center(
child: DropdownButtonExample(),
),
),
);
}
}
class DropdownButtonExample extends StatefulWidget {
const DropdownButtonExample({super.key});
@override
State<DropdownButtonExample> createState() => _DropdownButtonExampleState();
}
class _DropdownButtonExampleState extends State<DropdownButtonExample> {
String dropdownValue = list.first;
@override
Widget build(BuildContext context) {
return DropdownButton<String>(
value: dropdownValue,
//icon: const Icon(Icons.arrow_downward),
elevation: 16,
style: const TextStyle(color: Colors.deepPurple),
underline: Container(
height: 2,
color: Colors.deepPurpleAccent,
),
onChanged: (String? value) {
// This is called when the user selects an item.
setState(() {
dropdownValue = value!;
});
},
selectedItemBuilder: (context) =>
List.generate(1,
(i) => 
const SizedBox(
width: 50,
child: Icon(Icons.flag)
)
),
items: list.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: SizedBox(
width: 100,
child: Row(
mainAxisSize: MainAxisSize.min,
children: [const Icon(Icons.flag), Text(value)],
),
),
);
}).toList(),
);
}
}