Mastering Navigator 2.0 for Declarative Routing in Flutter

Introduction

Flutter Navigator 2.0 brings a powerful, declarative routing API that replaces the classic imperative push/pop model. With Navigator 2.0 you describe the current navigation stack as application state. The framework then renders pages to match that state. In this intermediate tutorial you will master Flutter Navigator 2.0, build a custom RouteInformationParser, RouterDelegate, manage route state, and handle deep links—all without wrestling with imperative calls.

Understanding RouteInformationParser and RouterDelegate

The two pillars of a Navigator 2.0 setup are:

RouteInformationParser: Converts a browser URL (or platform route information) into a typed configuration object.

RouterDelegate: Takes that configuration and builds the corresponding Navigator widget stack.

Key steps:

• Parse incoming URLs into your RoutePath model.

• Notify your app state when a new URL is parsed.

• Recreate the navigation stack inside your delegate’s build method.

Example Dart snippet:

// Simplified parser + delegate
class MyRouteParser extends RouteInformationParser<RoutePath> {
  @override
  Future<RoutePath> parseRouteInformation(
      RouteInformation info) async => RoutePath.fromUri(Uri.parse(info.location!));
}

class MyRouterDelegate extends RouterDelegate<RoutePath>
    with ChangeNotifier {
  RoutePath _path = RoutePath.home();
  @override
  RoutePath get currentConfiguration => _path;

  @override
  Widget build(BuildContext context) {
    return Navigator(
      pages: [
        MaterialPage(child: HomeScreen()),
        if (_path.isDetails) MaterialPage(child: DetailsScreen(id: _path.id)),
      ],
      onPopPage: (route, result) {
        _path = RoutePath.home();
        notifyListeners();
        return route.didPop(result);
      },
    );
  }

  @override
  Future<void> setNewRoutePath(RoutePath path) async {
    _path = path;
  }
}

Building Declarative Route State

Your app state should be a single source of truth for navigation. Typically:

• Extend ChangeNotifier or use ValueNotifier.

• Expose a setter for new paths that internally calls notifyListeners().

• Read the state in RouterDelegate.build to assemble the Navigator.pages list.

Example of a minimal AppState:

class AppState extends ChangeNotifier {
  RoutePath _path = RoutePath.home();
  RoutePath get path => _path;
  set path(RoutePath p) {
    _path = p;
    notifyListeners();
  }
}

Inject AppState via InheritedWidget, Provider, or any DI solution. The delegate listens to AppState changes and rebuilds.

Integrating with the Router Widget

Switch from MaterialApp to MaterialApp.router. Supply your parser, delegate, and optional BackButtonDispatcher:

final parser = MyRouteParser();
final delegate = MyRouterDelegate()..addListener(() => setState(() {}));

MaterialApp.router(
  routeInformationParser: parser,
  routerDelegate: delegate,
  backButtonDispatcher: RootBackButtonDispatcher(),
);

This widget handles:

• Converting taps on links or browser back/forward into calls to setNewRoutePath.

• Updating the URL when your delegate’s currentConfiguration changes.

Handling Deep Links and Browser URLs

To support web and deep links:

• Implement restoreRouteInformation in your parser to convert RoutePath back into RouteInformation.

• Listen for platform route changes on mobile via WidgetsBindingObserver.

• Use Router.neglect if you need to update internal state without triggering URL sync.

Example override for URL updates:

@override
RouteInformation restoreRouteInformation(RoutePath path) {
  final uri = path.toUri();
  return RouteInformation(location: uri.toString());
}

This ensures the browser URL always matches your current navigation stack.

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Conclusion

By mastering Flutter Navigator 2.0 you gain full control over routes, deep links, and web navigation in a declarative, state-driven manner. You’ll replace scattered Navigator.push calls with a clean, predictable routing architecture. Practice by adding nested navigators, guarded routes (e.g., authentication checks), and animated page transitions. The combination of RouteInformationParser, RouterDelegate, and an app-wide route state will serve as a solid foundation for any complex Flutter application.