Navigator.of( context )未导航，在context上出现空值错误

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('Navigator Example')),
        body: MyHomePage(),
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: ElevatedButton(
        onPressed: () async {
          await Future.microtask(() {
            Navigator.of(context).push(
              MaterialPageRoute(builder: (context) => SecondPage()),
            );
          });
        },
        child: Text('Go to Second Page'),
      ),
    );
  }
}

class SecondPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Second Page')),
      body: Center(child: Text('This is the second page')),
    );
  }
}