flutter:如何在不同的情况下跳转到不同的页面？

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Home'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('跳转到页面A'),
          onPressed: () {
            Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => PageA()),
            );
          },
        ),
      ),
    );
  }
}

class PageA extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Page A'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('跳转到页面B'),
          onPressed: () {
            Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => PageB()),
            );
          },
        ),
      ),
    );
  }
}

class PageB extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Page B'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('返回首页'),
          onPressed: () {
            Navigator.pop(context);
          },
        ),
      ),
    );
  }
}