I made a simple app for Android and I want to make it open source, What license should I use, how should I implement it in the project files, and is there anything else I need to take into consideration. 
What license should I use for an open source Android app that has no third party libraries outside of ones provided by the Android operating system?
license recommendation
I believe you can choose any license you want, it is written by you. You'd have to check if the libraries you use (or even Android as a platform) has some say in this, but I doubt it very much.