I’m having an issue where `RecyclerView` scroll po...

# android

[Mark]

I’m having an issue where RecyclerView scroll position is being nondeterministically ‘forgotten’ due to the adapter being updated via the collection of a StateFlow (in `Fragment.onCreateView()`:

val myAdapter = // create it
viewModel.itemsFlow.collectInViewScope(this) { items ->
    myAdapter.setItems(items)
}
recyclerView.adapter = myAdapter

As a workaround (which seems to work), I just delay setting the adapter until the first search results come in:

viewModel.itemsFlow.collectInViewScope(this) { items ->
    myAdapter.setItems(items)
    with(recyclerView) {
        if (adapter == null) {
            adapter = myAdapter
        }
    }
}

However, this feels like a hack. What is the correct way to collect adapter items and update the adapter so that the scroll position is not lost (when returning from a downstream fragment)?

[Joost Klitsie]

Even though this has nothign to do with kotlin, I usually do this:

viewModel.itemsFlow.collectInViewScope(this) { items ->
    with(recyclerView) {
        (adapter as? SomeAdapter)?.updateItems(items) ?: run {
             adapter = SomeAdapter(items)
             layoutManager = LinearLayoutManager(context)
        }
    }
}

It makes sure that the adapter gets initialized with an initial list, and after that the adapter gets updated so it can do its animations

[Adam Powell]

you might play around with this API which controls when state gets restored: https://developer.android.com/reference/kotlin/androidx/recyclerview/widget/RecyclerView.Adapter?hl=en#setstaterestorationpolicy

[Mark]

Thanks Adam, that answers my question perfectly.