v4 scroll position is not restored

[coonmoo]

Bug Report

Ionic Info

Ionic:

   ionic (Ionic CLI)          : 4.0.0-rc.9 (C:\Users\xxxx\AppData\Roaming\npm\node_modules\ionic)
   Ionic Framework            : @ionic/angular 4.0.0-alpha.7
   @angular-devkit/core       : 0.7.0-rc.0
   @angular-devkit/schematics : 0.7.0-rc.0
   @angular/cli               : 6.1.0-rc.0
   @ionic/ng-toolkit          : 1.0.0-rc.9
   @ionic/schematics-angular  : 1.0.0-rc.9

System:

   NodeJS : v10.5.0 (C:\Program Files\nodejs\node.exe)
   npm    : 5.2.0
   OS     : Windows 10

Describe the Bug
The scroll position is not restored when navigating back from a page.
If you scroll down a list and then navigate to a detail page and then hit the back button, the scroll position on the originating page is set back to [0, 0], basically loosing the context.
This behaviour is really bad for the user experience.

Steps to Reproduce

1. Run ionic serve
2. On home page wait until the list loads and scroll down to e.g. to the last list entry.
3. Click on the list entry and then navigate back from the detail page to the home page.
4. After navigating back the scroll position is set to [0,0], the previously scroll state is not restored.

Related Code
Example reproduction: https://github.com/coonmoo/IonicScrollPosBug

Expected Behavior
The scroll position should be correctly restored when navigating back from a page.

Additional Context
I tried to fix it with the latest Angular 6.1.0 feature of scrollPositionRestoration, but it does not seem to work. Angular's ViewportScroller always reports [0,0] scroll position when navigating back. I suppose that is an Ionic issue, because using plain Angular it seems to work (see also angular/angular#24547).

[MarkChrisLevy]

@coonmoo Because ionic uses its own content scrolling component ion-scroll, there has to be implementation of ViewportScroller (angular/common), that will handle scroll position restoration. Angular's default implementation uses window's scroll and that is the reason why it is not working with ionic right now. So, for now, you can implement your very own ViewportScroller and provide in your app module, hopefully ionic will have it implemented as well someday :-)

[coonmoo]

Thanks alot! Your implementation of the ViewportScroller so far rworks like a charm!

Anyway, would be nice to have Ionic providing an implementation, since this is a crucial requirement for most apps.

[bashoogzaad]

What is the latest status of this? Should I implement a ViewPortScroller or are you guys at Ionic working on a solution?

[rdlabo]

+1
I also want to know about this Issue.

[ptitjes]

@coonmoo Would you mind to share your implementation of ViewPortScroller ?

[naveedahmed1]

Any update on this?

[joanroig]

Seems like I have the same issue, I've described it here:
https://forum.ionicframework.com/t/ionic-4-returning-to-previous-page-loses-scroll-position/140886
After some research, I've tried the same scrollPositionRestoration as @coonmoo with no success in lastest version 4.0.0-beta.7

[joanroig]

My current workaround for this:
https://github.com/joanroig/Ionic4-restore-scroll-position