Adding a custom view to a page not working in PDFTron.Android for Xamarin

I’m trying to use PDFTron for Xamarin Android. I want to render and paint my custom annotations, without using their annotation system. According to their documentation in https://www.pdftron.com/documentation/xamarin/guides/ui-customization/custom-view/android/ You can add a CustomRelativeLayout which doesn’t work. It basically renders nothing in top of the PDF

enter image description here

I hosted the whole solution in here http://s000.tinyupload.com/index.php?file_id=14574507524295393508 so it’s easy to test and see if someone can see what’s wrong.

Thanks!

Please kindly try to only post the same question once on one platform. I will continue answering this question on SO:
https://stackoverflow.com/questions/60710395/adding-a-custom-view-to-a-page-not-working-in-pdftron-android-for-xamarin

Thanks.