DropdownMenu

 import "package:flutter/material.dart";

List<String> list = <String>["One","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten"];
void main()
{
  runApp(MyApp());
}
class MyApp extends StatelessWidget
{
  MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "DropDownMenu",
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.teal,
      ),
      home: DropDownDemo(),
    );
  }
}
class DropDownDemo extends StatefulWidget
{
  DropDownDemo({super.key});
  @override
  State<DropDownDemo> createState() {
    return DropDownDemoState();
  }
}
class DropDownDemoState extends State<DropDownDemo>
{
  String dropdownValue = list.first;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("DropDownDemo"),
        centerTitle: true,
      ),
      body: Center(
        child: DropdownButton<String>(
          value: dropdownValue,
          icon: const Icon(Icons.arrow_drop_down),
          elevation: 16,
          style: const TextStyle(color: Colors.deepPurple),
          underline: Container(
            height: 2,
            color: Colors.deepPurpleAccent,
          ),
          onChanged: (String? value) {
            setState(() {
              dropdownValue = value!;
            });
          },
          items: list.map<DropdownMenuItem<String>>((String value) {
            return DropdownMenuItem<String>(
              value: value,
              child: Text(value),
            );
          }).toList(),
        ),
      ),
    );
  }
}