如何在flutter中创建选择选项？

import 'package:flutter/material.dart';

String selectedOption;

DropdownButton(
  value: selectedOption,
  items: [
    DropdownMenuItem(
      value: 'Option 1',
      child: Text('Option 1'),
    ),
    DropdownMenuItem(
      value: 'Option 2',
      child: Text('Option 2'),
    ),
    DropdownMenuItem(
      value: 'Option 3',
      child: Text('Option 3'),
    ),
  ],
  onChanged: (value) {
    setState(() {
      selectedOption = value;
    });
  },
)

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('DropdownButton Example'),
        ),
        body: Center(
          child: DropdownButtonExample(),
        ),
      ),
    );
  }
}

class DropdownButtonExample extends StatefulWidget {
  @override
  _DropdownButtonExampleState createState() => _DropdownButtonExampleState();
}

class _DropdownButtonExampleState extends State<DropdownButtonExample> {
  String selectedOption;

  @override
  Widget build(BuildContext context) {
    return DropdownButton(
      value: selectedOption,
      items: [
        DropdownMenuItem(
          value: 'Option 1',
          child: Text('Option 1'),
        ),
        DropdownMenuItem(
          value: 'Option 2',
          child: Text('Option 2'),
        ),
        DropdownMenuItem(
          value: 'Option 3',
          child: Text('Option 3'),
        ),
      ],
      onChanged: (value) {
        setState(() {
          selectedOption = value;
        });
      },
    );
  }
}