How to scroll to the bottom of a RecyclerView? scrollToPosition doesn't work

Question

I was looking at this post to find the answer but... I think everyone on this post was facing the same scenario as me: scrollToPosition() was fully ignored, for an evident reason.

What I was using?

recyclerView.scrollToPosition(items.size());

... what WORKED?

recyclerView.scrollToPosition(items.size() - 1);

Just set setStackFromEnd=true or setReverseLayout=true so that LLM will layout items from end.

The difference between these two is that setStackFromEnd will set the view to show the last element, the layout direction will remain the same. (So, in an left-to-right horizontal Recycler View, the last element will be shown and scrolling to the left will show the earlier elements)

Whereas setReverseLayout will change the order of the elements added by the Adapter. The layout will start from the last element, which will be the left-most in an LTR Recycler View and then, scrolling to the right will show the earlier elements.

Sample:

final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
linearLayoutManager.setReverseLayout(true);
_listView.setLayoutManager(linearLayoutManager);

See documentation for details.

I know its late to answer here, still if anybody want to know solution is below

conversationView.smoothScrollToPosition(conversationView.getAdapter().getItemCount() - 1);

To scrolldown from any position in the recyclerview to bottom

Kotlin

editText.setOnClickListener {
    rv.postDelayed({                 
        rv.scrollToPosition(rv.adapter.itemCount - 1)
    }, 1000)
}

Java

edittext.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                rv.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                      rv.scrollToPosition(rv.getAdapter().getItemCount() - 1);
                    }
                }, 1000);
            }
        });

Add this code after sending message and before getting message from server

recyclerView.scrollToPosition(mChatList.size() - 1);

When you call setAdapter, that does not immediately lay out and position items on the screen (that takes a single layout pass) hence your scrollToPosition() call has no actual elements to scroll to when you call it.

Instead, you should register a ViewTreeObserver.OnGlobalLayoutListener (via addOnGlobalLayoutListner() from a ViewTreeObserver created by conversationView.getViewTreeObserver()) which delays your scrollToPosition() until after the first layout pass:

conversationView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
  public void onGlobalLayout() {
    conversationView.scrollToPosition(GENERIC_MESSAGE_LIST.size();
    // Unregister the listener to only call scrollToPosition once
    conversationView.getViewTreeObserver().removeGlobalOnLayoutListener(this);

    // Use vto.removeOnGlobalLayoutListener(this) on API16+ devices as 
    // removeGlobalOnLayoutListener is deprecated.
    // They do the same thing, just a rename so your choice.
  }
});

Solution for Kotlin:

apply below code after setting "recyclerView.adapter" or after "recyclerView.adapter.notifyDataSetChanged()"

recyclerView.scrollToPosition(recyclerView.adapter.itemCount - 1)