Here is some idle speculation re: APKs generated by App Inventor, Whether there is something like "middleware" that is attached to an app inventor "code/instructions" to make an APK is your 800lbs gorilla in the corner. If this is truly Java under the covers, then perhaps it would be possible to extract code. My guess is something else that more easily translates the blocks and shapes and such to code, and is understood and easily compiled (C/C++", Python, ????)