Java JNA Wrapper

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Effort to create a Java JNA (Java Native Access) wrapper for libfreenect.

Contents

About

See https://jna.dev.java.net/

Who is involved

Coordinator/Development: Mark Renouf

Current Status

See https://github.com/OpenKinect/libfreenect/pull/131

Compilation

Maven

If you have Maven (http://maven.apache.org/) installed, compiling could be as easy as:

$ cd ./wrappers/java/
$ mvn package

RedHat/Fedora Linux

These are command line instructions and don't make many assumptions about configuration Java class paths or native library paths. Since only one JAR (jna.jar) and one native library (libfreenect) are needed, we assume that you'll put a copy of each in a relative path directory. This could be made even simpler if your classpath and library environment variables are properly tuned, but this approach should work they are not.

1. Install libfreenect based RedHat/Fedora instructions here: http://openkinect.org/wiki/Installation/Compilation_Guides Note that you probably don't have to go beyond the "clone the repository" step, but probably a good idea to make sure that glview is working before proceeding.
2. Move to the Java wrapper directory:

$ cd ./wrappers/java/

3. Make a ./lib directory and a ./jars directory
4. Download jna.jar into ./jars (available from https://jna.dev.java.net/servlets/ProjectDocumentList)
5. Copy the libfreenect library (e.g. libfreenect.so.0.0.1) into ./lib
6. Build the libfreenect JNA jar:

$ rm -r ./tmpjar
$ mkdir ./tmpjar
$ javac -d ./tmpjar -classpath ./jars/jna.jar ./src/main/java/org/openkinect/freenect/*.java
$ jar -cvf ./jars/freenect-jna.jar -C tmpjar org
$ rm -r ./tmpjar

Demo

import org.openkinect.freenect.*;
 
public class JNATest {
 
    public static void main(String[] args) throws InterruptedException {
 
    	// DECLARATIONS
	        Context ctx = null;
	        Device dev = null;
 
    	// INITIALIZE DEVICE
	        ctx = Freenect.createContext();
	        if (ctx.numDevices() > 0) {
	            dev = ctx.openDevice(0);
	        } else {
	            System.err.println("No kinects detected.  Exiting.");
	            System.exit(0);
	        }
 
	    // TILT UP, DOWN, & RETURN
	        dev.setTiltAngle(20);
	        Thread.sleep(4000);
	        dev.setTiltAngle(-20);
	        Thread.sleep(4000);
	        dev.setTiltAngle(0);
 
	    // SHUT DOWN
	        if (ctx != null)
	            if (dev != null) {
	                dev.close();
	            }
	        ctx.shutdown();
    }
 
}

These instructions assume that you've followed the Compilation instructions above and have created ./wrappers/java/jars and ./wrappers/java/lib with the appropriate files.

1. Save as JNATest.java in ./wrappers/java/
2. Compile:

$ javac -classpath ./jars/freenect-jna.jar JNATest.java

3. Execute:

$ su -c "java -Djna.library.path=./lib -classpath .:./jars/jna.jar:./jars/freenect-jna.jar JNATest"

This demo should tilt the Kinect up 20 degrees, wait 4 seconds, tilt it down 40 degrees (20 degrees from level), wait 4 seconds, and return to level.

Sample Code

See ./wrappers/java/src/test/java/org/openkinect/freenect/FreenectTest.java

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