Android applications should always be neatly organized with a clear folder structure that makes your code easy to read. The way to do this is to logically group related things together into sub-packages within your application. Make sure every app has the following subpackages:

• com.example.myapp.activities - Contains all activities
• com.example.myapp.adapters - Contains all custom adapters
• com.example.myapp.models - Contains all our data models
• com.example.myapp.fragments - Contains all fragments
• com.example.myapp.helpers - Contains all helpers (custom code that supports the app).
• com.example.myapp.interfaces - Contains all interfaces

Keeping these folders in each app means that code is logically organized and scanning the code is a pleasant experience.

• http://blog.smartlogicsolutions.com/2013/07/09/organizing-your-android-development-code-structure/