在展开ExpansionTile小部件时更改标题文本的颜色

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('ExpansionTile Example')),
        body: ExpansionTileExample(),
      ),
    );
  }
}

class ExpansionTileExample extends StatefulWidget {
  @override
  _ExpansionTileExampleState createState() => _ExpansionTileExampleState();
}

class _ExpansionTileExampleState extends State<ExpansionTileExample> {
  bool _isExpanded = false;

  @override
  Widget build(BuildContext context) {
    return ListView(
      children: [
        ExpansionTile(
          title: Text(
            'Click me to expand',
            style: TextStyle(
              color: _isExpanded ? Colors.blue : Colors.black,
            ),
          ),
          onExpansionChanged: (expanded) {
            setState(() {
              _isExpanded = expanded;
            });
          },
          children: [
            ListTile(title: Text('Item 1')),
            ListTile(title: Text('Item 2')),
            ListTile(title: Text('Item 3')),
          ],
        ),
      ],
    );
  }
}