A short introduction to the new AAR library format for android app projects. Talk on Droidcon 2014

1. Get started with AAR archives
How to create and work with the new AAR archive format using gradle and android studio

2. René Mertins
Senior Java Architect with more then 10 years experience.
Architect of the apponsormonetization platform.
Email: r.mertins@bitforce-it.de
g+: +ReneMertinsHH
www.apponsor.com
www.bitforce-it.de

3. WTF is AAR?
-Introduced I/O 2013
-Library project packaging format
-AAR is Android ARchive

4. It‘s a simple zip

5. Benefits
1.Never handle complete library projects any more
2.No need to publish a library in source

6. For distributors
-Provide precompiled
-Optimized and obfuscated for best performance
-Be more sure that no one changes what shouldn‘t changed
-Easer publishing and distribution over maven

7. For developers
-reference like support lib or play services
-Clean project structure
-Online update if remote repository

8. Actual situation
-Full copies of lib projects in source
-Reference by file path
-Build every time with your app
-Difficult to optimize and obfuscate
-Difficult to manage different lib versions

9. Actual situation
-Full copies of lib projects in source
-Reference by file path
-Build every time with your app
-Difficult to optimize and obfuscate
-Difficult to manage different lib versions

10. Actual situation
-Full copies of lib projects in source
-Reference by file path
-Build every time with your app
-Difficult to optimize and obfuscate
-Difficult to manage different lib versions

11. The idea
compile 'com.actionbarsherlock:actionbarsherlock:4.4.0@aar‚
compile 'com.jeremyfeinstein.slidingmenu.lib:slidingmenu:1.3@aar'
-Library projects are separated from app projects
-Published as desired in to AAR
-App developer only declare dependencies

12. Good to know
Or how we failed the first time

13. Creating AAR is easy
-Create lib project
-Call „bundleRelease“

14. But now?
-Place in project structure? Fail
-Gradle include? Fail
-Gradle file dependency? Fail

15. The trick
-Provide as maven repo like google does
-Publish into maven repo is easy with gradle
-Reference AAR in access able repositories
-New trick, import

16. The trick
-Provide as maven repo like google does
-Publish into maven repo is easy with gradle
-Reference AAR in access able repositories
-New trick, import

17. The trick
-Provide as maven repo like google does
-Publish into maven repo is easy with gradle
-Reference AAR in access able repositories
-New trick, import

18. A working example
Decide what‘s next: live coding or slides ?

19. Start a library
Use the project wizard to create an initial android library project.

20. Add something useful
I added a static method which returns „Hello [name]! How are you?“

21. Tweak gradle
-Add the android-maven plugin
-Apply adroid-maven and maven plugin
-Define maven meta data
-Define upload archive task

22. Use gradle tasks
-Call bundleReleaseto create AAR in build folder
-Call uploadArchivesto upload the AAR to your locale repository

23. review
That’s the repository created by gradle task „uploadArchives“

24. A new app
Create a simple app to test our library.

25. Define dependency
-Apply the maven plugin
-Define your locale repository
-Setup the dependency to the new library

26. Use it

27. Test

28. Note
A referenced AAR library is not shown in Android Studio.
You can use the library, you get auto completion etc.
But you can it inspect it in the project structure!
For Support-Lib and some other stuff from google it‘s working.
I‘m sure it will come in future.
One point I want to address!

29. Hint
Martin Liersch who is well known for his gradle build system talk is providing a maven repository where he places a lot of useful library projects as AAR artifacts.
GitHub: https://github.com/Goddchen/mvn-repo
Repo URL: https://github.com/Goddchen/mvn-repo/raw/master/

30. Hint
The gradle project webpage includes a very good documentation.
http://www.gradle.org/docs/current/userguide/userguide.html
In the maven plugin chapters is a part about uploading artifacts to repositories. Also explaining using different transports like ssh to a remote repository.
http://www.gradle.org/docs/current/userguide/maven_plugin.html# uploading_to_maven_repositories

31. Observe
Without the android-maven plugin this solution would be much more complicated.
You can find the project at gitHub
https://github.com/dcendents/android-maven-plugin

32. Pull requests
Most off the public library projects for android can be found on github.
Nearly all are still using ADT and are not providing AAR artifacts.
But most often there is a smart guy already done the work to port to android studio and make it easy to publish an aar. So look up the pull requests for your favorite lib and you will find a fork for android studio.
Like stefanrusk did for andengine:
https://github.com/stefanrusek/AndEngine/tree/GLES2

33. Hint
In one of the last releases of Android Studio they added an import feature for aarpackages.
When that happens? I don’t know…
You can find it over:
File -> New Module -> Import JAR or AAR package
New way to define dependency in gradle.build
artifacts.add("default", file('myedulibrary-0.1.aar'))
In 0.9.x is not working,
updated in 1.0 rc1 not tested

34. Hint
Inspect an aarlibrary in your app project.
There is trick to do that.
1. Close all open files.
2. Select your app module in project view
3. switch to structure view
Then you will see your aarlibrary expanded in the tree view.

35. Thank you
Feel free to approach me for any question.
r.mertins@bitforce-it.de
G+: ReneMertinsHH