page_router 0.0.3

A router that uses Flutter's Navigator 2.0

page_router

Experimental router for Flutter built using the Navigator 2.0 API.

Usage

class _PageRouterExampleState extends State<PageRouterExample> {
  final routerData = PageRouterData({
    '/': RoutePath(
      builder: (context, params) => FadeTransitionPage(
        key: ValueKey('/'),
        child: HomeScreen(),
      ),
    ),
    '/users/:id': RoutePath(
      validator: idValidator,
      builder: (context, params) => MaterialPage(
        key: ValueKey('/users/:id'),
        child: UserScreen(userId: params[':id']),
      ),
    ),
    '/users/:id/preferences': RoutePath(
      validator: idValidator,
      builder: (context, params) => FadeTransitionPage(
        key: ValueKey('/users/:id/preferences'),
        child: UserPreferencesScreen(
          userId: params[':id'],
        ),
      ),
    ),
  });

  Validator idValidator = (params) async {
    var id = int.tryParse(params[':id']);
    return id != null && id < 100;
  };

  @override
  Widget build(BuildContext context) {
    return PageRouter(
      data: routerData,
      child: MaterialApp.router(
        title: 'page_router Example App',
        routerDelegate: routerData.routerDelegate,
        routeInformationParser: routerData.informationParser,
      ),
    );
  }
}

OutlinedButton(
  child: Text('Go to User 123'),
  onPressed: () {
    PageRouter.of(context).pushNamed('/users/123');
  },
),

See the example/ application for a complete example

Known Issues / Unsupported features

• Hierarchical Routing (see section below)
• Displaying subroutes on the same screen
• Validation
• Including pages on the stack

Issue: Hierarchical Routing

Right now, this package requires each route to be defined up-front:

  final routerData = PageRouterData({
    '/': RoutePath(
      builder: (context, params) => FadeTransitionPage(
        key: ValueKey('/'),
        child: HomeScreen(),
      ),
    ),
    '/users/:id': RoutePath(
      builder: (context, params) => MaterialPage(
        key: ValueKey('/users/:id'),
        child: UserScreen(userId: params[':id']),
      ),
    ),
    '/users/:id/preferences': RoutePath(
      builder: (context, params) => FadeTransitionPage(
        key: ValueKey('/users/:id/preferences'),
        child: UserPreferencesScreen(
          userId: params[':id'],
        ),
      ),
    ),
  });

Sometimes, parts of the app are built separately, with separate routes. For example, Team A might define routes for the app, but rely on Team B to define routes for a part of the app.

To support this use-case, a routing package can add support for hierarchical routing. For example:

library app;
import 'team_b.dart';

var routerData = PageRouterData({
  '/': RoutePath(
    builder: (context, params) => MaterialPage(
      child: Scaffold(
        body: Center(
          child: Text('home screen'),
        ),
      ),
    ),
    subroutes: {
      '/teamB': teamBRoutePath,
    },
  ),
});

library team_b;

var teamBRoutePath = RoutePath(
  builder: (context, params) => MaterialPage(
    child: Scaffold(
      body: Center(
        child: Text("Team B's widget"),
      ),
    ),
  ),
  subroutes: {
    '/details': RoutePath(
      builder: (context, params, child) {
        return MaterialPage(
          child: Scaffold(
            body: Center(
              child: Text('details screen'),
            ),
          ),
        );
      },
    ),
  },
);

The entrypoint for an app needs to decide how to structure the subroutes for an app, but leaves the underlying route structure to the library / package being imported.

Issue: Displaying subroutes on the same screen

Some apps may need to display the child. In this example, both the "My App" Text widget and the "Details" Text widget are displayed in the Column when the app navigates to '/details':

library app;

var routerData = PageRouterData.hierarchical({
  '/': RoutePath(
    childBuilder: (context, params, child) => MaterialPage(
      child: Scaffold(
        body: Column(
          children: [
            Text('My App'),
            child,
          ],
        ),
      ),
    ),
    subroutes: {
      '/details': RoutePath(
        builder: (context, params) {
          return MaterialPage(
            child: Scaffold(
              body: Center(
                child: Text('Details'),
              ),
            ),
          );
        },
      ),
    },
  ),
});

Issue: Validation

Before a route is navigated to, the app may choose to validate that the route is valid. For example, checking if a user exists before showing a page:

var routerData = PageRouterData({
  '/users/:id': RoutePath(
    validator: (params) async {
      // If this is `false`, the route isn't navigated to.
      var exists = await _checkIfUserExists(params[':id']);
      return exists;
    },
    builder: (context, params) => MaterialPage(
      child: Scaffold(
        body: Center(
          child: Text('User ID: ${params[":id"]}'),
        ),
      ),
    ),
  ),
});

If the validation failed, a call to PageRouter.of(context).pushNamed('/users/123') will return false, perhaps with a result object containing a message.

Issue: Including pages on the stack

Right now, all underlying pages are cleared when a page is navigated to (either by a linking directly via deep link or but manually updating the URL).

Instead, RoutePaths should be able to be configured to be included underneath by adding a flag

library app;

var routerData = PageRouterData.hierarchical({
  '/': RoutePath(
    // Indicate that this page should be included when any page underneath is
    // routed to.
    includeInPageStack: true, 
    builder: (context, params) {
      return MaterialPage(
        child: Scaffold(
          body: Center(
            child: Text('Details'),
          ),
        ),
      );
    },
  ),
  '/details': RoutePath(
     builder: (context, params) {
       return MaterialPage(
         child: Scaffold(
           body: Center(
             child: Text('Details'),
           ),
         ),
       );
     },
   ),
  ),
});