It is available on Github:
With Android Studio you can write Processing/Java code (includes Google Cardboard SDK libraries) to build Android 3D/VR apps for your phone. The above photo is a screenshot from a test app in the code repository on Github showing the viewer lens distortion correction feature.
I also fixed a problem displaying line and text (among others graphics) where the left image was written to the right eye viewport. I determined this only occurred when invoking beginShape()...endShape(), but not createShape(). I got a clue about how to fix this in a Processing Forum at
With the announcement of Google Cardboard SDK for Android v0.7.0, Google also announced Google Cardboard SDK for iOS v0.7.0. So now with Processing also available for Apple iOS, it seems there may be a way to write processing-cardboard code and port to iOS. Unfortunately I'm not experienced with Apple iOS development, so it is not something I can do for now and Cardboard SDK iOS is not coded in Java.
For more information about Processing see www.processing.org