Hi, I've got a new different doubt (sorry about asking so much xD but I'm quite a newbie...). I'm using blob detection and everything seems to work ok. I managed to draw the centroids of the detected blobs to check if everything was working OK and it did. Now I've got a new strange problem...

Using this code:


//Copy centroids into an array
for (int ii= 0; ii<myDetector.getBlobNb () ; ii++){
 Blob myBlob = myDetector.getBlob(ii);            // Check every detected blob
 if(((myBlob.w*width)*(myBlob.h*height)) > 1500){ // if the blob is bigger than 1500 pixels
   
 centroid[centroidN][0] = myBlob.x*width;         // Save it's centroid into an array
 centroid[centroidN][1] = myBlob.y*height;
 centroidN = centroidN+1;
 
 }
}

I get this error in the line painted red:

NullPointerException

Exception in thread "Animation Thread" java.lang.NullPointerException
     at sketch_aug28a.draw(sketch_aug28a.java:118)
     at processing.core.PApplet.handleDraw(PApplet.java:1406)
     at processing.core.PApplet.run(PApplet.java:1311)
     at java.lang.Thread.run(Unknown Source)


I can run the program without any problem or error, but when a blob enters the frame it blocks and I get that error.
Does someone know why I might be getting it? :S

Thanx BenHem!! it did help ^^ I got rid of my error, but now I'm getting:

ArrayIndexOutOfBoundsException : 2

Exception in thread "Animation Thread" java.lang.ArrayIndexOutOfBoundsException: 2
     at sketch_aug28a.draw(sketch_aug28a.java:118)
     at processing.core.PApplet.handleDraw(PApplet.java:1406)
     at processing.core.PApplet.run(PApplet.java:1311)
     at java.lang.Thread.run(Unknown Source)

Which PhiLho talks about in his reply to other post saying:

"Oh, and you want to put a limit on nodecount! Otherwise you will get another exception: ArrayOutOfBounds."

In my case I suppose that means I should limit "centroidN". But I think I already do :S. By limiting it, he means for example, setting it to 0 again some time right?

Before I check a new frame, my code ends with:

   centroidN = 0;
   updatePixels();

And I've made the program so it doesnt take into count every blob, just blobs bigger than 1500pixels... so it shouldnt exceed the limit I think, should it? :S

(Or maybe PhiLho means something else by putting a limit to that variable? )

Thanx again

PD: I've just checked something. The program works ok while there is only 1 blob, it only crashes when it detects 2 blobs or more.

Louen wrote on Aug 28^th, 2009, 12:01pm:

In that case, it was to stop incrementing the counter...

Quote:
Here, 2 is the value of index causing the exception. That means you have an array of size 2, ie. accepting indexes of 0 and 1.