onActivityReenterMediaSharedElementCallback.java

final MediaSharedElementCallback sharedElementCallback = new MediaSharedElementCallback();
getActivity().setExitSharedElementCallback(sharedElementCallback);
getActivity().supportPostponeEnterTransition();
mRecyclerView.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
    @Override
    public boolean onPreDraw() {
        mRecyclerView.getViewTreeObserver().removeOnPreDrawListener(this);
        RecyclerView.ViewHolder holder =     mRecyclerView.findViewHolderForAdapterPosition(position);
        if (holder instanceof GalleryAdapter.MediaViewHolder) {
            GalleryAdapter.MediaViewHolder mediaViewHolder = (GalleryAdapter.MediaViewHolder) holder;
            sharedElementCallback.setSharedElementViews(mediaViewHolder.mImageView, mediaViewHolder.mCheckView);
        }
        getActivity().supportStartPostponedEnterTransition();
        return true;
    }
});