Flutter transition using Navigator 2.0

main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  bool isLoggedIn = false;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        // iOS behaviour on all platforms:
        // platform: TargetPlatform.iOS,
      ),
      home: Navigator(
        pages: [
          if (isLoggedIn)
            MaterialPage<void>(
              key: ValueKey(1),
              child: Scaffold(
                backgroundColor: Colors.blue,
              ),
            )
          else
            MaterialPage<void>(
              key: ValueKey(2),
              child: Scaffold(
                backgroundColor: Colors.orange,
                body: Center(
                  child: ElevatedButton(
                    onPressed: () => setState(() {
                      isLoggedIn = true;
                    }),
                    child: Text('Log in'),
                  ),
                ),
              ),
            ),
        ],
        onPopPage: (Route<dynamic> route, dynamic result) {
          // ...
          return route.didPop(result);
        },
      ),
    );
  }
}