screen rebuilds when using coordinator (resolved, open issue for reference only)

[YuryMorozov2001]

Hi! Thanks for this amazing package and the great work you’ve done!
I noticed that when using coordinator.push/pop, screens are being rebuilt even when its not necessary. Maybe we should use caching. Do you have any ideas on how we can fix this?

2025-12-07.21.00.07.mov

To detect which widgets are being rebuilt, I used this code

2025-12-07.21.02.10.mov

Also, if the widget in the router is declared as const, there are no unnecessary rebuilds:

2025-12-07.21.16.11.mov

Demo code

import 'package:flutter/material.dart';
import 'package:routing/flutter_scan.dart';
import 'package:zenrouter/zenrouter.dart';

void main() {
  runApp(const MainApp());
}

final appCoordinator = AppCoordinator();

class MainApp extends StatelessWidget {
  const MainApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routerDelegate: appCoordinator.routerDelegate,
      routeInformationParser: appCoordinator.routeInformationParser,
    );
  }
}

abstract class AppRoute extends RouteTarget with RouteUnique {}

class AppCoordinator extends Coordinator<AppRoute> {
  @override
  AppRoute parseRouteFromUri(Uri uri) {
    return switch (uri.pathSegments) {
      [] => HomeRoute(),
      ['profile', String userId] => ProfileRoute(userId),
      _ => NotFoundRoute(),
    };
  }
}

class NotFoundRoute extends AppRoute {
  @override
  Uri toUri() => Uri.parse('/not-found');

  @override
  Widget build(Coordinator<AppRoute> coordinator, BuildContext context) {
    return Scaffold(body: Center(child: Text('Not found')));
  }
}

class NotFoundPage {}

class HomeRoute extends AppRoute {
  @override
  Uri toUri() => Uri.parse('/');

  @override
  Widget build(AppCoordinator coordinator, BuildContext context) {
    return HomeScreen();
    // return const HomeScreen();
  }
}

class ProfileRoute extends AppRoute {
  ProfileRoute(this.userId);
  final String userId;

  @override
  List<Object?> get props => [userId];

  @override
  Uri toUri() => Uri.parse('/profile/$userId');

  @override
  Widget build(AppCoordinator coordinator, BuildContext context) {
    return ProfilePage(userId: userId);
  }
}

class HomeScreen extends StatelessWidget {
  const HomeScreen({super.key});
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Text('Home Page'),
            Text(DateTime.now().toString()),
            Builder(
              builder: (context) {
                return TextButton(
                  onPressed: () {
                    appCoordinator.push(ProfileRoute('123'));
                  },
                  child: Text('Go to profile'),
                );
              },
            ),
          ],
        ),
      ),
    );
  }
}

class ProfilePage extends StatelessWidget {
  const ProfilePage({super.key, required this.userId});

  final String userId;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisSize: .min,
          children: [
            Text('User ID: $userId'),
            TextButton(
              onPressed: () {
                Navigator.pop(context);
              },
              child: Text('back'),
            ),
          ],
        ),
      ),
    );
  }
}  

[definev]

Thank you for reporting issue 💙 I will take a look on it. First of all i think it's expected behaviour since whole screen is moving when the top route popped.
I encourage separate the view from build function since it will help reduce render by nature of const widget but i will check the behaviour on Navigator and NavigationStack to see is the same happened 👍

[medz]

#9 (comment)

@definev I'm having the same problem, and it doesn't seem like what you said in your reply on X. I've spent an hour on this and still haven't solved it 😂

[medz]

Thank you for reporting issue 💙 I will take a look on it. First of all i think it's expected behaviour since whole screen is moving when the top route popped. I encourage separate the view from build function since it will help reduce render by nature of const widget but i will check the behaviour on Navigator and NavigationStack to see is the same happened 👍

I don't believe this is expected behavior; it's incorrect. (The hierarchy also occurs on the go_router shell, and I'm not sure if it's been fixed. I haven't followed go_router in a long time.)

For example, the following code:

/users/:name/profile                   /users/:name/posts 
┌──────────────────┐                  ┌──────────────────┐
│ UserLayout       │                  │ UserLayout       │
│ ┌──────────────┐ │                  │ ┌──────────────┐ │
│ │ Profile      │ │  ────────────>   │ │ Posts        │ │
│ │              │ │                  │ │              │ │
│ └──────────────┘ │                  │ └──────────────┘ │
└──────────────────┘                  └──────────────────┘

When I go from /user/johnny/profile -> /user/johnny/posts, UserLayout shouldn't be rebuilt. This is completely wrong (if it rebuilds).

[definev]

I investigated and this is definitely the issue as @medz said. Rendering should not trigger re-rendering in UserLayout. I think this issue is related to inner coordinator listening somewhere. I will find the root cause of the issue.

[medz]

I investigated and this is definitely the issue as @medz said. Rendering should not trigger re-rendering in UserLayout. I think this issue is related to inner coordinator listening somewhere. I will find the root cause of the issue.

The only condition that should trigger a UserLayout to be rebuilt is when it reads route parameters through some API, such as params, query, or hash, and these parameters are actually modified. If it is just a layout, such as one that simply adds a menu bar and the body directly renders the child elements, then rebuilding it is meaningless.

[definev]

I fixed it in the next version 🚀
The problem is when recreating Page object internally it build whole list again every single time. The solution is reuse it if possible so the route don't need to create brand new Page for each iteration 👍
cc: @YuryMorozov2001 @medz

Yury usecase:

Before:

before_optimize.mp4

After:

after_optimize.mp4

Medz usecase:

usecase.mp4

[YuryMorozov2001]

@definev thank you for the quick fix! Great job 🔥

[definev]

Reopen this issues since @YuryMorozov2001 found an unexpected rebuilt in IndexedStackPath when pushing new screen in root path.

[YuryMorozov2001]

I noticed that if we replace .material to .cupertino, everything works as expected

[definev]

I confirm @YuryMorozov2001 said is correct, there're something wrong with MaterialPage.

material_bug.mp4

[definev]

I think i found the root cause here. The root cause is using difference kind of Page in the root layout, in the HomeLayout i demonstrate the way to use custom page transition here even for Layout. That why when we set it all .cupertino it works like normal and when set .material it rebuild when enter and exit screen.

I create a reproduce issue project here and test 4 routing ways: go_router, auto_route, zenrouter and plain Navigator 2.0. This is the bug inside Page API of flutter framework. (I filed an issue for that flutter/flutter#179975)
https://github.com/definev/rebuild_page_bug