如何根据flutter中选择的下拉项添加文本字段值

import 'package:flutter/material.dart';

class MyForm extends StatefulWidget {
  @override
  _MyFormState createState() => _MyFormState();
}

class _MyFormState extends State<MyForm> {
  String selectedOption;
  TextEditingController textEditingController = TextEditingController();

  List<String> dropdownOptions = [
    'Option 1',
    'Option 2',
    'Option 3',
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Add Text Field Value'),
      ),
      body: Padding(
        padding: EdgeInsets.all(16.0),
        child: Column(
          children: [
            DropdownButton(
              value: selectedOption,
              items: dropdownOptions.map((String option) {
                return DropdownMenuItem(
                  value: option,
                  child: Text(option),
                );
              }).toList(),
              onChanged: (String newValue) {
                setState(() {
                  selectedOption = newValue;
                });
              },
            ),
            SizedBox(height: 16.0),
            TextField(
              controller: textEditingController,
              decoration: InputDecoration(
                labelText: 'Text Field',
              ),
            ),
            SizedBox(height: 16.0),
            RaisedButton(
              child: Text('Add Value'),
              onPressed: () {
                String selectedValue = selectedOption ?? '';
                String textFieldValue = textEditingController.text;
                String result = '$selectedValue $textFieldValue';
                print(result);
              },
            ),
          ],
        ),
      ),
    );
  }
}