Losing nested scroll position when scrolling parent

Hello!

I have a vertical list composed of multiple nested horizontal lists. If I scroll my horizontal list and then scroll vertically my list, I sometime lost the scroll position of my nested horizontal list.

Losing nested position demo: 1- scrolling “A voir aussi” to Calls as first fully displayed item 2- scrolling “Sous couverture” to Strike Back as first fully displayed item 3- scroll down 4- scroll up: “A voir aussi” scrolling position is ok but “Sous couverture” isn’t, it display as first item “Killing Eve”

Here is my code: https://github.com/loutry/EpoxySample/commits/lost-nesting-position-on-rebind

I’m using EpoxyRecyclerView everywhere and I enable saveViewState.

I also followed the discussions https://github.com/airbnb/epoxy/issues/561 but I didn’t successfully fix my problem.

[eboudrant]

Your RowGroupView is a LinearLayout and Epoxy is saving its state only (with saveViewState = true) . To restore scroll position you need to manually save/restore the state of the inner EpoxyRecyclerView from your RowGroupView.

As a quick fix try something like :

class RowGroupView : LinearLayout {
    ...
    override fun onSaveInstanceState(): Parcelable? {
        return recycler.onSaveInstanceState()
    }

    override fun onRestoreInstanceState(state: Parcelable?) {
        recycler.onRestoreInstanceState(state)
    }
}

[loutry]

Hi again! I end up fixing my problem by relying on ViewGroup and ViewStub as state in the documentation: https://github.com/airbnb/epoxy/wiki/Grouping-Models.

Here is the updated branch on the sample: https://github.com/loutry/EpoxySample/tree/viewstub

Our custom layout manager was indeed not compliant regarding state restoration but nothing that we can’t manage on or own 😃

Thanks a lot for your guidance and time!