A pushReplacementNamed navigation with arguments.

push-replacement-named-with-args.dart

import 'package:flutter/material.dart';

void main() {
  runApp(
    MaterialApp(
      debugShowCheckedModeBanner: false,
      initialRoute: '/',
      routes: {
        '/': (context) => AuthService(),
        '/dash': (context) => DashBoardScreen(),
      },
    ),
  );
}

class AuthService extends StatelessWidget {
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Auth Service Screen')),
      body: Center(
        child: RaisedButton(
          child: Text("Login!", style: TextStyle(fontSize: 20)),
          onPressed: () => Navigator.pushReplacementNamed(
            context,
            '/dash',
            arguments: {"name": "Foo Bar", "email": "foobar@baz.com"},
          ),
        ),
      ),
    );
  }
}

class DashBoardScreen extends StatelessWidget {
  Widget build(BuildContext context) {
    Map<String, String> args = ModalRoute.of(context).settings.arguments;
    return Scaffold(
      appBar: AppBar(title: Text('Dash Board Screen')),
      body: Center(
        child: Text(
          "Name: ${args['name']}\nEmail: ${args['email']}",
          style: TextStyle(fontSize: 20),
        ),
      ),
    );
  }
}