如何根据选中的Dropdownbutton项在列中有条件地创建文本子项？

import 'package:flutter/material.dart';

class MyDropdownList extends StatefulWidget {
  @override
  _MyDropdownListState createState() => _MyDropdownListState();
}

class _MyDropdownListState extends State<MyDropdownList> {
  String selectedOption;
  List<String> options = ['Option 1', 'Option 2', 'Option 3'];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Dropdown List Example'),
      ),
      body: Column(
        children: [
          DropdownButton<String>(
            value: selectedOption,
            onChanged: (String newValue) {
              setState(() {
                selectedOption = newValue;
              });
            },
            items: options.map<DropdownMenuItem<String>>((String value) {
              return DropdownMenuItem<String>(
                value: value,
                child: Text(value),
              );
            }).toList(),
          ),
          SizedBox(height: 20),
          Expanded(
            child: ListView.builder(
              itemCount: options.length,
              itemBuilder: (BuildContext context, int index) {
                if (selectedOption == null || selectedOption == options[index]) {
                  return ListTile(
                    title: Text(options[index]),
                  );
                } else {
                  return Container(); // 不满足条件时返回空容器
                }
              },
            ),
          ),
        ],
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: MyDropdownList(),
  ));
}