Example of the 'routes table' and the pushedNamed() function.

navigate_with_named_routes.dart

import 'package:flutter/material.dart';

void main() => runApp(NavigateNamedRoutes());

class NavigateNamedRoutes extends StatelessWidget {
  @override
  Widget build(BuildContext context) => MaterialApp(
        title: 'Named Routes Demo',
        initialRoute: '/',
        routes: {
          '/': (context) => FirstScreen(),
          '/second': (context) => SecondScreen(),
        },
        onGenerateRoute: Router.generateRoute,
      );
}

class FirstScreen extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _FirstScreenState();
}

class _FirstScreenState extends State<FirstScreen> {
  /// Displayed at the center of the screen.
  dynamic data = '';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('First Screen'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            ElevatedButton(
                child: const Text('Second screen'),
                onPressed: () async {
                  data = await Navigator.pushNamed(context, '/second');
                  setState(() {});
                }),
            ElevatedButton(
                child: const Text('Third screen'),
                onPressed: () async {
                  data = await Navigator.pushNamed(context, '/third',
                      arguments: 'argument!');
                  setState(() {});
                }),
            ElevatedButton(
                child: const Text('Fourth screen'),
                onPressed: () async {
                  data = await Navigator.pushNamed(context, '/fourth',
                      arguments: 'argument!');
                  setState(() {});
                }),
            Text(
              "${data ?? ''}",
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
    );
  }
}

class SecondScreen extends StatelessWidget {
  final title = 'Second Screen';
  @override
  Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(
          title: Text(title),
        ),
        body: Center(
          child: ElevatedButton(
            onPressed: () => Navigator.pop(context, title),
            child: const Text('Go back!'),
          ),
        ),
      );
}

class ThirdScreen extends StatelessWidget {
  ThirdScreen({Key key, this.arguments}) : super(key: key);
  final Object arguments;
  final title = 'Third Screen';
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: () => Navigator.pop<String>(context, "$title ${arguments ?? ''}"),
          child: const Text('Go back!'),
        ),
      ),
    );
  }
}

class FourthScreen extends StatelessWidget {
  FourthScreen({Key key, this.arguments}) : super(key: key);
  final Object arguments;
  final title = 'Fourth Screen';
  @override
  Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(
          title: Text(title),
        ),
        body: Center(
          child: ElevatedButton(
            onPressed: () => Navigator.pop(context, "$title ${arguments ?? ''}"),
            child: const Text('Go back!'),
          ),
        ),
      );
}

class Router {
  /// passed to the widget, MaterialApp
  static Route<T> generateRoute<T>(RouteSettings settings) {
    var func;
    switch (settings.name) {
      case '/third':
        func = (_) => ThirdScreen(arguments: settings.arguments);
        break;
      case '/fourth':
        func = (_) => FourthScreen(arguments: settings.arguments);
        break;
      default:
        func = (_) => Scaffold(
              body:
                  Center(child: Text('No route defined for ${settings.name}')),
            );
    }
    return _pageRoute(func);
  }

  static _pageRoute(WidgetBuilder builder) =>
      MaterialPageRoute(builder: builder);
}