Bluetooth Arduino Connection apps

Hi! I have recently download a Bluetooth Arduino Connection apps (https://play.google.com/store/apps/details?id=appinventor.ai_pmosconi.BTArduinoConnection&hl=zh-TW). And I want to know more about the code about it. But I only find code for App Inventor(.aia). May I ask where I can find the code of java so I can open it from Android Studio? Thank you.