Scala on Android Revisited

One of the biggest drawbacks of using Scala on Android is the additional required treeshake / proguard step. This is necessary to keep the app size down since Scala has quite a big runtime library. Depending on the size of the application and dependencies this can easily add an extra 30 seconds on top of the normal build process which slows down the development cycle drastically.

However there is a way around that: you can tweak the emulator to include predexed versions of the Scala runtime, which means you can completely skip the proguard step during the (development) build. Together with sbt’s incremental compilation this makes for really fast build times, not much slower compared to a standard Java build. Needless to say this makes a huge productivity difference because you can iterate a lot faster.