How to decompile an APK or DEX file on Android platform? [closed]

You need Three Tools to decompile an APK file.

1. Dex2jar - Tools to work with android .dex and java .class files

2. ApkTool - A tool for reverse engineering Android apk files

3. JD-GUI - Java Decompiler is a tools to decompile and analyze Java 5 “byte code” and the later versions.

for more how-to-use-dextojar. Hope this will help You and all! :)

Online APK Decompiler
http://www.decompileandroid.com/
https://www.decompiler.com/
APK Decompiler App for Windows
http://forum.xda-developers.com/showthread.php?t=2493107

Update 2015/12/04
ClassyShark you can open APK/Zip/Class/Jar files and analyze their contents. https://github.com/google/android-classyshark

Update 2021/1/28
https://ibotpeaches.github.io/Apktool/
https://github.com/skylot/jadx