@Override
        public void onChanged() {
            invalidateAllScrollOffsets();
        }
Set the FastScroll Popup position. This is either {@link FastScroller.FastScrollerPopupPosition#ADJACENT},
meaning the popup moves adjacent to the FastScroll thumb, or {@link FastScroller.FastScrollerPopupPosition#CENTER},
meaning the popup is static and centered within the RecyclerView.
android/third_party/recyclerview-fastscroll/src/main/java/com/simplecityapps/recyclerview_fastscroll/views/FastScrollRecyclerView.java