dialog_nested_navigation

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(
      navigatorKey: Utils.app1Nav,
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: App1(),
        ),
      ),
    );
  }
}

class App1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        const Text(
          'Hello, World!'
        ),
        TextButton(
          onPressed: () {
              showDialog(context: context,
                 builder: (BuildContext cxt) {
                   
                   return AlertDialog(
                    content: App2()
                   );
                 }        
              );
          },
          child: const Text('Click me to show dialog')
        )
      ]
    );
  }
}

class App2 extends StatelessWidget {
  
  @override
  Widget build(BuildContext context) {
    
    return Column(
        children: [
          Expanded(
            child: Navigator(
            key: Utils.app2Nav,
            initialRoute: '/app2page1',
            onGenerateRoute: (RouteSettings settings) {
              Widget page;

              switch(settings.name) {
                case '/app2page1':
                  page = App2Page1();
                  break;
                case '/app2page2':
                  page = App2Page2();
                  break;
                case '/app2page3':
                  page = App2Page3();
                  break;
                default:
                  page = App2Page1();
                  break;
              }

              return PageRouteBuilder(
                pageBuilder: (_, __, ___) => page,
                transitionDuration: const Duration(seconds: 0)
              );
            }
          ) 
          ),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              TextButton(
                onPressed: () {
                  Utils.app2Nav.currentState!.pushReplacementNamed('/app2page1');
                },
                child: const Text('Go To App2Page1')
              ),
              TextButton(
                onPressed: () {
                  Utils.app2Nav.currentState!.pushReplacementNamed('/app2page2');
                },
                child: const Text('Go To App2Page2')
              ),
              TextButton(
                onPressed: () {
                  Utils.app2Nav.currentState!.pushReplacementNamed('/app2page3');
                },
                child: const Text('Go To App2Page3')
              )
            ]
          )
        ]
    );
  }
}

class App2Page1 extends StatelessWidget {
  
  @override
  Widget build(BuildContext context) {
     return const Text('App 2 Page 1', style: TextStyle(fontSize: 30));
  }
}

class App2Page2 extends StatelessWidget {
  
  @override
  Widget build(BuildContext context) {
     return const Text('App 2 Page 2', style: TextStyle(fontSize: 30));
  }
}

class App2Page3 extends StatelessWidget {
  
  @override
  Widget build(BuildContext context) {
     return const Text('App 2 Page 3', style: TextStyle(fontSize: 30));
  }
}

class Utils {
  static GlobalKey<NavigatorState> app1Nav = GlobalKey();
  static GlobalKey<NavigatorState> app2Nav = GlobalKey();
}