The hard drive on my laptop just crashed and I lost all the source code for an app that I have been working on for the past two months. All I have is the APK file that is st
apktool is THE way to go. Online apktool service exists as well: http://www.javadecompilers.com/apktool
Some limitations, obviously, exist due to the service ‘online nature’: you may extract and research assets and the manifest file, but it is impossible to recompile the application at the moment.
Still, this is a no-hassle way to 'open' the android application.