You shouldn’t be messing with camera stuff in your Google Cardboard application since most google cardboard units cover the camera lense.
It’s not a feature you’ll see adopted anytime soon since different devices have the camera in different places making it unreliable to create a universal headset from.
Edit: Looks like the original google cardboard had a cutout for your camera and there are some apps that take advantage of this, but all models since then (star wars edition, Viewmasters) have not had a camera cutout.
solved Google carboard camera zoom [closed]