This tutorial is all about how you can edit an android .apk file easily with the help of he editor and other tools which I will be explaining one after the other for easy understanding.
Let take it that you found an awesome Android app and you wanted to play with the .apk file to add additional features or design to the app, all you need to do is to edit the .apk file but editing it is not that simple but can be done anyway.

How to Edit Android .apk file easily:
You can simply open it with winrar and extract files, usually you can play with png files or mp3/ogg,if you want to go further you can edit xml,smali or m10(for HTC only).
All I can say is that it was easier in the early android OS versions,now they are complicating things for security and patents but also to change more deep, u need the source code , and that's what we don't have though there are other tips on YouTube how to find the source codes of Android App apk file.

Secondly you can rename xml to html and open it using hex editor that will enable you read and be able to edit the APK file.