code: private void addAnimatingView(View view) {
          boolean alreadyAdded = false;
          if (mNumAnimatingViews > 0) {
              for (int i = mAnimatingViewIndex; i < getChildCount(); ++i) {
                  if (getChildAt(i) == view) {
                      alreadyAdded = true;
                      break;
                  }
              }
          }
          if (!alreadyAdded) {
              if (mNumAnimatingViews == 0) {
                  mAnimatingViewIndex = getChildCount();
              }
              ++mNumAnimatingViews;
              addView(view);
          }
          mRecycler.unscrapView(getChildViewHolder(view));
      }
docs: Adds a view to the animatingViews list.
  mAnimatingViews holds the child views that are currently being kept around
  purely for the purpose of being animated out of view. They are drawn as a regular
  part of the child list of the RecyclerView, but they are invisible to the LayoutManager
  as they are managed separately from the regular child views.
  @param view The view to be removed