dropdown_list

import 'package:flutter/material.dart';

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatefulWidget {
  
  MyWidgetState createState() => MyWidgetState();
}

class MyWidgetState extends State<MyWidget> {
  
  String dropdownvalue1 = '--';
  String dropdownvalue2 = '--';
  
  @override
  Widget build(BuildContext context) {
    return Column(
        children: [
          DropdownButton<String>(
              value: dropdownvalue1,
              items: <String>['--','A', 'B', 'C', 'D']
                  .map((String value) {
                return DropdownMenuItem<String>(
                  value: value,
                  child: Text(value),
                );
              }).toList(),
              onChanged: (String? newValue) {
                setState(() {
                  dropdownvalue1 = newValue!;
                });
              }),
          DropdownButton<String>(
              value: dropdownvalue2,
              items: <String>['--','E', 'F', 'G', 'H']
                  .map((String value) {
                return DropdownMenuItem<String>(
                  value: value,
                  child: Text(value),
                );
              }).toList(),
              onChanged: (String? newValue) {
                setState(() {
                  dropdownvalue2 = newValue!;
                });
              }),
        ],
      );
  }
}