I recently spent some time trying out Scala on Android, with good results. One of the things I wanted to get working on the Android platform was the Akka actor library, unfortunately this was not exactly a simple affair.

The ProGuard tool, which is a necessary part of the Scala-Android toolchain, needs configuration to make Akka work properly. While I found several ProGuard configurations for Akka online, I was not able to get any of them to work with the versions of Scala and Akka I was using. In the end, I had to manually debug the config with a cycle of building my project with Akka code included, then uploading my code to an android emulator. Once the code was running, I would wait for it to crash with a runtime exception, which would tell me what class was missing. I could then update my ProGuard config, rinse, and repeat.

Eventually I ended up with the following ProGuard configuration which allowed me to use use Akka 2.1.0 with Scala 2.10.1 on Android:

-keep class com.typesafe.**
-keep class akka.**
-keep class scala.collection.immutable.StringLike {
    *;
}
-keepclasseswithmembers class * {
    public <init>(java.lang.String, akka.actor.ActorSystem$Settings, akka.event.EventStream, akka.actor.Scheduler, akka.actor.DynamicAccess);
}
-keepclasseswithmembers class * {
    public <init>(akka.actor.ExtendedActorSystem);
}
-keep class scala.collection.SeqLike {
    public protected *;
}

I used this code to implement the “Suggest” examples from Ed Burnette’s “Hello Android” book using scala and Akka actors. The code for this project, including the full proguard config I used is on Github.