Android App Decompiler is a useful Tool to unextract and decompiles Android APK. When you runed the Decompiler than created an folder with all Files from then APK and the dex (dalvik executable format) being converted to an jar file. You must only now use an Java Decompiler like jd-gui and you have all files of the App.
After a program has been thrown into the world in binary form, it can boomerang back as source code. The Boomerang reverse engineering framework is the first general native executable decompiler available to the public.