How To Develop iPhone Applications in Java for Distribution (Without Jailbreaking)

iPhone is a great phone to develop applications for. Unfortunately Apple decided to restrict developing iPhone applications in a less known language called Objective C, which is used pretty much within Apple (and by Apple developers) and almost noweher else. Only Steve Jobs knows the reason behind this strange decision. Java ( J2ME) is the most popular language & platform for mobile development. So Java developers need a way to develop applications for iPhone too by leveraging their core competency.

Previously I have provided two ways how Java developers can install, compile and run iPhone applications on Java. Today I will present a third method.

Apple’s SDK for the iPhone, as you know, is based on Objective-C as the development language as well as Cocoa for the GUI.
Unfortunately Apple’s super-restrictive license agreement for the iPhone SDK prohibits the porting of the Java virtual machine to the iPhone. Today we will talk about how we can use Open Source Java to run applications which will run on Apple’s iPhone. The open source project by Arno Puder, Associate Professor at the San Francisco State University, uses a cross-compiler to convert Open Source Java code to Objective-C and provide a Java-based implementation of the Cocoa library. With the help of these tools, iPhone applications can be written in pure Java.

Using the Java version of Cocoa, it is possible to run a Java-based iPhone application as a Java desktop/applet application that can be cross-compiled to run natively on the iPhone.

You can find more details about the software from https://www.xmlvm.org/

XmlVM’s SourceForge.net Subversion repository can only be checked out through SVN with the following instruction set:

svn co https://xmlvm.svn.sourceforge.net/svnroot/xmlvm xmlvm

Warning: This is a generic Subversion checkout command which will pull all modules, tags and/or branches of the project. In most cases, you will want to add ‘/trunk‘ to the HTTPS URL above to check out only trunk (main development line).

Each of the boxes in the diagram above represents an artifact while the arrows denote the various transformations between those artifacts. The input to the XMLVM toolchain is either a Java class file or a .NET executable. A Java class file is translated to XMLVM_JVM which is an XML-document describing the contents of that class file. Likewise XMLVM_CLR is an XML-document describing the contents of a .NET executable. XMLVM_CLR can be cross-compiled to XMLVM_JVM with the help of a data flow analysis (DFA) which is shown as XMLVM_CLR-DFA in the figure below. XMLVM_JVM serves as a canonical representation as it acts as a boundary between the front- and back-end of the cross-compiler. Once XMLVM_JVM has been generated, it can be mapped to various high-level programming languages. It is also possible to map XMLVM_JVM to a Java class file again.

Check it out. Also don’t forget to read the detailed guide on how to install, compile & run Java applications on iPhone.