AAR format is a jar file containing a compiled Android Library project. Here's some info on what is inside an AAR file
What this means for app developers is that instead of (the old way):
- Downloading the source code of a library project
- Building it in eclipse
- Setting your application project to depend on the local library project
You can instead add the dependency specification to your project/app/build.gradle's dependencies block: compile 'fr.baloomba:viewpagerindicator:2.4.2'
Then gradle (on the next build) searches for the aar file in a central binary repository, downloads the library and allows you to use it's functionality in your project. ( ex: http://search.maven.org/remotecontent?filepath=fr/baloomba/viewpagerindicator/2.4.2/viewpagerindicator-2.4.2.aar )
You can also search the central repository's web interface for libraries to depend on. Once you've clicked on a library to add to the project, click "Gradle/Grails" under "Dependency Information" to copy the line to add to build.gradle.
In my opinion this is a huge improvement.
You don't need to add any permissions to the app, either way, adding a Library project dependency is a compile time thing, not runtime or user-facing.