在flutter应用程序中应用主题数据不会更改Appbar颜色、工具栏颜色、文本、字体和按钮

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        primaryColor: Colors.blue,
        appBarTheme: AppBarTheme(
          color: Colors.blue,
          textTheme: TextTheme(
            headline6: TextStyle(color: Colors.white, fontSize: 20),
          ),
        ),
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Theme Demo'),
      ),
      body: Center(
        child: Text('Hello World!'),
      ),
    );
  }
}

appBar: AppBar(
  title: Text('Flutter Theme Demo', style: Theme.of(context).textTheme.headline6),
  backgroundColor: Theme.of(context).primaryColor, // 确保这里没有覆盖主题颜色
),

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  ThemeData _themeData = ThemeData.light();

  void _changeTheme() {
    setState(() {
      _themeData = _themeData == ThemeData.light() ? ThemeData.dark() : ThemeData.light();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Theme(
      data: _themeData,
      child: Scaffold(
        appBar: AppBar(
          title: Text('Flutter Theme Demo'),
        ),
        body: Center(
          child: Text('Hello World!'),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: _changeTheme,
          child: Icon(Icons.color_lens),
        ),
      ),
    );
  }
}

appBar: AppBar(
  title: Text('Flutter Theme Demo', style: TextStyle(color: Colors.white, fontSize: 20)!important),
),