I suggest to write the article (it can be useful to yourself to pin down your experience and go back to the project later!), but to wait a little, a new Wiki is coming to replace the old Hacks section.

I'm now trying to create a simple to use library, instead of using the Main.java file with Processing.

In the Main.java I had:

Code:

package libnfcjava;

public class Main {

    static {
        System.load("C:\\RFIDtest\\code\\libnfc.dll");
        System.load("C:\\RFIDtest\\code\\LibNFCNative.dll");
    }

    public Main() {
    }

    public static void main(String[] args) {
    }

    public native String nativeTagID();
    public native boolean nativeConnectedRFID();
} 

I accessed the native functions (JNI) from within Processing by doing (for example):

boolean RFIDON = new Main().nativeConnectedRFID();


For the Processing library I now have a slightly different .java:

Code:

package libnfc;

import processing.core.PApplet;

public class LibNFC {

    PApplet myParent;
	
    public final String VERSION = "0.1.0";

    static {
       System.load("C:\\RFIDtest\\code\\libnfc.dll");
       System.load("C:\\RFIDtest\\code\\LibNFCNative.dll");
    }	

    public LibNFC(PApplet theParent) {
        myParent = theParent;
    }

    public String version() {
        return VERSION;
    }

    public boolean isOn() {
        boolean status = this.nativeConnectedRFID();
        return status;
    }

    public String tagID() {
        String tag = this.nativeTagID();
        return tag;
    }
	
    public native String nativeTagID();
    public native boolean nativeConnectedRFID();
} 

But when I try to run this example:

Code:

import libnfc.*;

LibNFC rfid;

void setup() {
  rfid = new LibNFC(this);
  
  size(400, 400);
  background(255);
}

void draw() {
   rectMode(CENTER);
	
   while(rfid.isOn()) {
     stroke(0);
     fill(255);
     rect(200,200,100,100);
   
     String tag = rfid.tagID();
   
     if(tag.equals("0400ae51962281")) {
       stroke(0);
       fill(127,0,0);
       rect(200,200,100,100);
     } else if(tag.equals("04ece051962280")) {
         stroke(0);
	 fill(255,200,200);
	 rect(200,200,100,100);
     } else {
       stroke(0);
       fill(255);
       rect(200,200,100,100);
     }
   }
   background(255);
} 

I get the following error as soon I get to the while(rfid.isOn()):

UnsatisfiedLinkError: libnfc.LibNFC.nativeConnectedRFID()Z

PhiLho  wrote on Mar 9^th, 2010, 1:36am:


Adding a println before and after rfid = new LibNFC(this); prints two strings correctly, giving me the same error in while(rfid.isOn()).

If I had the dlls in the library folder, together with the jar, how should I write the System.load

Is it possible that the error is from the way I call the native functions from within my methods Ex.:

Code:

boolean status = this.nativeConnectedRFID(); 

PhiLho  wrote on Mar 9^th, 2010, 2:35pm:


Thanks anyway. If I had the dlls in the library folder, together with the jar, how should I write the System.load so it would work on any computer

PhiLho  wrote on Mar 10^th, 2010, 9:29am:


Using System.loadLibrary("name.dll"); works fine, thanks

I've managed to get the library working, I had the recompile my dlls with some changes.