CodenameOne Project : Finally Java on the iPhone

I periodically monitor the progress of multi-platform development solutions for the mobile space. As a Java developer, I’m especially interested in solutions to bring Java to the iPhone. Even better would be a Java solution that will run on all of the major devices (Android, iOS, and Blackberry).

CodenameOne is the most promising project to appear in this space so far. It includes an API, a GUI designer, and a build/deployment solution so that you can develop your application in 100% pure Java then a native application on most major platforms (including iOS, Android, RIM, Windows Phone 7, and J2ME). The API forms a thin abstraction over the native libraries on each platform so many components are heavy-weight. This allows the applications to take on the native look and feel of the host system. The underlying mechanics work differently for each platform. E.g. on Android, the Java runs on the built-in VM, whereas iPhone builds use XMLVM to convert the Java bytecode to native code.

So far I haven’t done very much with it (just discovered it last night). I downloaded the Netbeans plugin which adds the ability to create a “Codename One Project” within Netbeans. This includes a GUI editor with a few themes to get you jump started with some common application structures. My initial test application was just a default tabbed application. It took me 2 minute to create it.
The Netbeans plugin includes an iPhone emulator so that you can test the application right inside netbeans. In my initial tests, this seemed to work quite well. Building the application was a single click.

I’m a little wary of the build process, as it occurs on their server. Apparently the Java is compiled to byte-code on your local machine, then it is sent to their server to have it converted to a native application. This requires that you sign up for a free account. After signing up for an account, and logging in, it said that I could perform up to 80 builds before upgrading. It didn’t say whether this is 80 per month, 80 per year, or 80 total — but I didn’t look into it too deeply. The build process took a little while (more than 20 minutes — I just requested the build, then waited 20 minutes and went to bed). In the morning the build was ready for download.

I was quite impressed with the file size. It was only 6.9 megs. Yes this was just a simple app with 4 tabs, some buttons, and forms, but this size is still quite good. Especially considering that it includes all code necessary from the Java libraries in order to run. I was expecting it to come in around 50 megs, as I fully expected the whole JVM to be statically compiled into it. Luckily, it looks like they use some optimizations to remove dead and unused code before building it.


Pros: Java. Support for most major devices. Good documentation. Good IDE support (both Netbeans and Eclipse). Easy, one-click-builds, Support for signing so you can submit apps to their respective app stores. Open Source (GPL 2. With Classpath Exception — free for commerical/non-commericial use)

Cons: Building is done in the cloud. This is convenient but it opens the door to problems in that you are now dependent upon them. They say that you can build it yourself and that there is information on the net on how to do this – but they offer no support for it.

Hopefully I’ll have the opportunity to build my first app with this in the next couple of weeks.


  • Codename One Website
  • How CodenameOne Works (a Stackoverflow discussion).
  • XMLVM – The underlying tool that allows them to cross-compile Java to native code.
  • LWUIT – A toolkit for user interfaces on mobile devices of which CodenameOne is a descendent.
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