The app folder

Wow! As you can see, a lot of stuff goes on just to create an application. Now, we are going to finally discuss the App folder structure; this folder is where we will spend the majority of our development time. We shall explore what the different types of files are for and how they are used to create an application. Since this is the primary development folder and contains your entire code base for your application, I would highly recommend you put this folder under source control and/or maintain backups of this folder. The App folder already contains a couple folders and a few files that are mentioned under the App folder files subsection. Let's look at both of these folders first and the files contained in them, and finally, we will look at each of the individual files in the App folder.

The .gradle folder

This folder is for the gradle build system; it basically only contains cache and data items that are used while the application is being built. This folder might be...