code: private void initPagerAnimator() {
          final SimpleTracker gridTracker = new SimpleTracker() {
              @Override
              public View getViewAt(int pos) {
                  RecyclerView.ViewHolder holder = views.grid.findViewHolderForLayoutPosition(pos);
                  return holder == null ? null : PhotoListAdapter.getImage(holder);
              }
          };
  
          final SimpleTracker pagerTracker = new SimpleTracker() {
              @Override
              public View getViewAt(int pos) {
                  RecyclePagerAdapter.ViewHolder holder = pagerAdapter.getViewHolder(pos);
                  return holder == null ? null : PhotoPagerAdapter.getImage(holder);
              }
          };
  
          listAnimator = GestureTransitions.from(views.grid, gridTracker)
                  .into(views.pager, pagerTracker);
  
          // Setting up and animating image transition
          listAnimator.addPositionUpdateListener(this::applyFullPagerState);
      }
docs: Initializing grid-to-pager animation.