It has been asked several times in the forum, but apple has always maintained that screenshot capture prevention is not supported, how is it that whatsapp and several financial apps are doing it, if screenshot capturing is not possible, its not DRM, is it the adding of a secured text as a layer on to the uiview layer? how have they designed a custom screen if that is the case? Also how is it getting approved by apple! If detection of airplay is possible and can be suppressed, why not screenshot?
There is no way to prevent screen capture with the public APIs currently available. If you'd like us to consider adding the necessary functionality, please file an enhancement request using Feedback Assistant. Once you file the request, please post the FB number here.
If you're not familiar with how to file enhancement requests, take a look at Bug Reporting: How and Why?