This demos the changes made to StfalconImageViewer made in this fork.
This app uses a custom ViewHolder to support videos as well as images and to overlay text on the scrolling ViewPager pages.
The CustomViewHolder ensures there is an ImageView and a VideoView for every page, and chooses at binding time which View to show. Both of these views are in a FrameLayout along with a TextView, which provides the text overlay.
A custom ViewHolderLoader (just a method reference, CustomViewHolder::buildViewHolder) is passed to the modified StfalconImageViewer to ensure CustomViewHolder is used.