Question

Ok im really struggling with unlocking my GUI which is locked due to separate SwingWorker thread. Basically what my program does: Initializes webcam, and then grabs single frame and displays it as JLabel icon (doing single grab+display on Button click is ease, however i have immense difficulties in doing such operation consecutively in order to do some image processing). I am aiming to obtain such result:

Grab frame -> process it -> display as ImageIcon of Jlabel > … repeat Grab frame >…

I need results while webcam is streaming, therefore i used SwingWorker publish and process. In my code "processing part" is not included as it is not necessary since i cant even obtain proper continuous frame grabbing. Generally my background thread will never finish unless cancelled (well thats the assumption as i want to process images as fast as possible with maximum frames per second – unless i should do it other way? – i guess separate thread for single frame grab&process would be bad idea due to fact that im aiming to get 10+ FPS). I know my SwingWorker thread works, since i made tests of saving consecutive images to C:\, and it did work, but my GUI is locked anyway, but at least i know that thread is running and grabbing frames.

Generally i have 2 problems:

• no JLabel icon update
• Locked GUI

My SwingWorker code:

private class FrameStream extends SwingWorker<Void, BufferedImage> { 
    @Override
    protected Void doInBackground() throws InterruptedException{
        BufferedImage processedImage = null;
        
        while (!isCancelled()) {
            processedImage = getPIC_COLOR(player);
            publish(processedImage);
            
            Thread.sleep(5000); // i made such delay to check whether program is not "choking" with data, but its not the case, without this delay everthing is the same
        }            
        return null;
    }

    @Override
    protected void process(List<BufferedImage> mystuff) {
        Iterator it = mystuff.iterator(); 

        while (it.hasNext()) {
            img_field.setIcon(new ImageIcon(mystuff.get(mystuff.size()-1)));
        }
    }

    @Override
    protected void done() {            
        infoBAR.setText("FINISHED");
    }
}

I am so desperate that i rewritten my code completely basing on tutorials example: Flipper as you can see it is ridiculously similar. All my previous efforts also locked gui so tried the ‘tutorial way’, nonetheless it did not work, which is a pity. Im in a dead end because i have no clue how to fix that. Im desperate for help since as you can see it seems exactly the same as the tutorial one, maybe something other causes issues: MY FULL CODE

Please help, i’m unable to solve it by myself.

Answer 1

One thing that looks a little different to me is your process method. Rather than specifying the last image, you might wish to iterate through all images like so:

  @Override
  protected void process(List<BufferedImage> mystuff) {
     for (BufferedImage bImage : mystuff) {
        img_field.setIcon(new ImageIcon(bImage));
     }
  }

I’m not sure if this will make a significant difference, but I believe that this is how process should be written. Another thought — if the BufferedImages are large you may wish to create the ImageIcon in the background thread and publish the ImageIcon rather than the BufferedImage.