But last week I helped Damon to finally support JRuby on his Android Scripting Environment (ASE).

• Downloaded JRuby sources (jruby-1.2.0RC1) from http://www.jruby.org/download.
• Patched the build.xml to not include doc/index.html from dynalang.jar otherwise dx will complain about an HTML page in the ruby-complete.jar.
  
  

  $ diff -r jruby-1.2.0RC1 jruby-1.2.0RC1.patched/
  Only in jruby-1.2.0RC1.patched/: build
  diff -r jruby-1.2.0RC1/build.xml jruby-1.2.0RC1.patched/build.xml
  42c42
  <
  ---
  >
  238c238,240
  <         <zipfileset src="${build.lib.dir}/dynalang-0.3.jar"/>
  ---
  >         <zipfileset src="${build.lib.dir}/dynalang-0.3.jar">
  >           <exclude name="**/doc/index.html"/>
  >         </zipfileset>
  268c270,272
  <         <zipfileset src="${build.lib.dir}/dynalang-0.3.jar"/>
  ---
  >         <zipfileset src="${build.lib.dir}/dynalang-0.3.jar">
  >           <exclude name="**/doc/index.html"/>
  >         </zipfileset>
  387c391,393
  <         <zipfileset src="${build.lib.dir}/dynalang-0.3.jar"/>
  ---
  >         <zipfileset src="${build.lib.dir}/dynalang-0.3.jar">
  >           <exclude name="**/doc/index.html"/>
  >         </zipfileset>

• Downloaded the JSON sources from http://rubyforge.org/frs/?group_id=953 and put them in lib/ruby/1.8/json/
• Copied android.rb to lib/ruby/1.8/.
• Built jar-complete (ant jar-complete) and added jruby-complete.jar to eclipse project.
• Connected the bits and pieces in com.google.ase.interpreter.jruby

But beware! The new ASE apk is HUGE (4.6M) and JRuby is fairly slow. But it works

At first I tried the easiest way and added the JRuby jar to my android project. This would have been way to easy and as I expected it did not work.

Then I copied all the JRuby sources into my android project and eclipse gave me more than 100 errors. I had to remove org.jruby.javasupport.bsf.BSFExample and the whole org.jruby.demo package because of dependencies to awt and swing. Now only a single error message was left with a dependency on some class I can’t remember in java.beans. So I downloaded the Java sources and copied the class into my project which gave me a few new dependencies. So I copied the whole java.beans package into the project and removed all dependencies to awt and swing from the code. Now I needed to add only 2 more classed com.sun.beans.ObjectHandler and sun.awt.EventListenerAggregate for eclipse to stop complaining.

At this point I encountered my first bug in Android: dx(the compiler for Dalvik) complained about the bsf.jar file which came with JRuby[1]. Fortunately I could work on with the 2.4.0 version of bsf.

At this point eclipse stopped complaining and dx was able to create Dalvik byte code for my test application and package the result.

But when I started the result on the emulator all I got was an exception… This is where I will stop for today and continue whenever I find some time. If someone out there has already successfully used JRuby on Android please leave me a comment on how you managed to do it.

[1] the bug was fixed less than 3h after I reported it. Kudos to the Dalvik team!

As you can see I’m toying around with the android SDK. I guess this will be my first 20 percent project here at Google.

So far I’m impressed with the state of the SDK. There is a ton of documentation and up to now everything worked at once.

I have a couple of ideas I would like to try on android but unfortunately all of them involve bluetooth and there is no bluetooth support for the emulator (yet?).

If you have a great idea you would like to see as an app for your next cellphone, just leave me a comment or implement it on your own