Refresh page `onBack`, sample code for https://github.com/flutter/flutter/issues/36530

main.dart

import 'package:flutter/material.dart';

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(
        scaffoldBackgroundColor: darkBlue,
      ),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatefulWidget {
  @override
  State<MyWidget> createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  @override
  Widget build(BuildContext context) {
    print('built');
    return Column(children: [
      Text(
        'Hello, World!',
        style: Theme.of(context).textTheme.headline4,
      ),
      TextButton(
        onPressed: () => Navigator.push(
          context,
          MaterialPageRoute(builder: (context) => SecondPage()),
        ).then((value) => setState(() {})),
        child: const Text('next'),
      ),
    ]);
  }
}

class SecondPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        automaticallyImplyLeading: true,
      ),
      body: const Center(
        child: Text('second page'),
      ),
    );
  }
}