滚动到RecyclerView中插入的项目

Question

I've made a RecylcerView (A) composed by ViewHolder containing another RecyclerView (B) . When an item is inserted/modified ( notifyItemInserted() / notifyItemChanged() ) in B I want A to scroll until the B item just inserted/modified appears on screen.

I've got the position of B in A and with that I get B and I retrive the last element, which is the one just inserted. When I call the findViewHolderForAdapterPosition I get NullPointerExeption .

My code:

RecyclerView B = ((MyAdapter.MyViewHolder)A
                    .findfindViewHolderForAdapterPosition(posB))
                    .getRecyclerViewB();
B.scrollToPosition(B.getAdapter().getItemCount()-1);

What am I doing wrong? Is this method right?

Answer 1

If this position is (far) beyond displayed area it will not have bound ViewHolder . Just use RecyclerView.scrollToPosition(int position) here.

Like A.scrollToPosition(positionOfB)

Answer 2

I use the layout manager on my Recycler view

fun setData(listItems: List<ItemDataModel>) {
            customAdapter.clear()
            customAdapter.addAll(listItems)
            (layoutManager as? LinearLayoutManager)?.scrollToPositionWithOffset(customAdapter.itemCount - 1, 0)
        }

-----Custom Adapter methods ----

 fun clear() {
        items.clear()
        notifyDataSetChanged()
    }

fun addAll(items: List<T>) {
        this.items.addAll(items)
        notifyItemRangeInserted(this.items.lastIndex, items.size)
    }