Hi Irina,
MoodleMobile is a PhoneGap/Cordova application. The development code is written in JavaScript, not in Java or Swift, but the code inside the "platforms" folder is native code that can be opened by IDEs like XCode and Android Studio.
I did a quick Google search about this and there are a lot of sites talking about this. For example:
http://www.tricedesigns.com/2013/05/16/phonegap-android-studio/
Kind regards,
Dani