Save scroll state in nested RecyclerView

Question

I have a problem in my application. I have main list (recycler view). This list keeps 20 horizontal recycler views. It looks really similar like Netflix app. I need to keep state of every "carousel" in main list. If I move first item to right, next to left, scroll down (first and second items are recycled), rotate the screen, scroll up, I need to have restored position of first and second element.

I know that I should use linearLayout.saveOnInstanceState and onRestoreState but my problem is that every carousel is in main list.

configChanges in AndroidManifest.xml can not come into play...

Thank you!

Answer 1

As @Ixx mentioned scrollX is always 0. You have to use layoutManager to save and restore scroll position

 val scrollStates = mutableMapOf<Int, Parcelable?>()
override fun onViewRecycled(holder: VH) {
    super.onViewRecycled(holder)

    val key = holder.layoutPosition
    scrollStates[key] = holder.childRecycler.layoutManager.onSaveInstanceState()
}

override fun onBindViewHolder(holder: VH, position: Int) {
    val key = holder.layoutPosition
    val state = scrollStates[key]
    if(state != null){
        holder.childRecycler.layoutManager.onRestoreInstanceState(state)
    }else{

        holder.childRecycler.layoutManager.scrollToPosition(0)
    }
}