Programatically Scroll at the last position of recyclerview on header click

Question

I had a view with a netstedScroll and a recyclerView that I was using to display my data so my fragment was like that:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto">
<androidx.core.widget.NestedScrollView
        android:id="@+id/scrollView"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toTopOf="parent">

<androidx.recyclerview.widget.RecyclerView
                android:id="@+id/recyclerView"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                tools:itemCount="10"
                tools:listitem="@layout/row_header" />
</androidx.core.widget.NestedScrollView>

The recyclerview had a custom adapter that I used is to get a recyclerview same as an expandable view (I didn't use the native one) and everything was great until my last update, so we decided to add more KPIs and informations on the recyclerview became at the very bottom of the view:

The problem now is when the user clicks on negociating, the list of products doesn't show automatically if he doesn't scroll manually, and feels like there isn't any changes. I want just on click of this part, to scroll, the problem is that I'm using a custom adapter:

private fun bindHeaderViewHolder(holder: RecyclerView.ViewHolder, position: Int, viewType: ViewType) {
        val dataIndex = viewType.dataIndex
        val headerViewHolder = holder as SectionHeaderViewHolder
        when(position){
           
            0 -> headerViewHolder.sectionTitle.text = "Sold out"
            1 -> headerViewHolder.sectionTitle.text = "Rent"
            2 -> headerViewHolder.sectionTitle.text = "On stock"
            3 -> headerViewHolder.sectionTitle.text = "Negociating"
        }
if (isExpanded(position)) {
            headerViewHolder.expandIcon.setImageResource(R.drawable.ic_expand_less_black_24dp)
            if(position == 3){
                Log.e("position delivered", "I'm here")
            }
        } else {
            headerViewHolder.expandIcon.setImageResource(R.drawable.ic_expand_more_black_24dp)
        }

Can someone help me or suggest a solution for that please?

Answer 1

You can connect a listener to the adapter and called it when needed indicating the clicked position within the adapter:

class YourAdapter(val changeItemListener: (Int) -> Unit) : RecyclerView.Adapter<YourViewHolder>() {
    ...
    changeItemListener(position)
    ...
}

After that you can from Activity or fragment create the adapter with the listener and within the listener you can call scrollToPosition or whatever you may need.

viewModelAdapter = YourAdapter(changeItemListener = {position -> your_recyclerview.smoothScrollToPosition(position)})