为在flutter中单击的每个按钮更改appBar

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

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

class _MyHomePageState extends State<MyHomePage> {
  AppBar appBar;

  @override
  void initState() {
    super.initState();
    appBar = AppBar(
      title: Text('Initial Title'),
    );
  }

  void changeAppBarTitle(String newTitle) {
    setState(() {
      appBar = AppBar(
        title: Text(newTitle),
      );
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: appBar,
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ElevatedButton(
              onPressed: () => changeAppBarTitle('Button 1 Clicked'),
              child: Text('Button 1'),
            ),
            ElevatedButton(
              onPressed: () => changeAppBarTitle('Button 2 Clicked'),
              child: Text('Button 2'),
            ),
          ],
        ),
      ),
    );
  }
}