Java Swing GUI freezes - observer pattern

Question

For a program I am creating I have used the observer pattern, yet whilst my Observable sends data almost constantly, simulated with a loop here because the actual code is hooked up to a device and measures the data, my update(); method runs as it should but swing doesn't.

Swing only updates the JTextField AFTER the loop has finished, yet when I use System.out.println() it iterates nicely each update.

Observable code:

public void collectData()
{

    for(int i = 0; i < 10; i++)
    {
        currRandom = (Math.random() * 10);
        for(Observer o : observers)
        {
            notify(o);
        }

    }
}

Observer (SWING) code:

public void update()
{
    jRecievedData.setText(jRecievedData.getText() + "\n" + Double.toString(PVC.pc.getCurr()));
    jlAverage.setText("Average: " + PVC.getAverage());
    jlMin.setText("Minimum: " + PVC.getMin());
    jlMax.setText("Maximum: "+ PVC.getMax());

    // setText updates slow
}

Any help would be greatly appreciated! (I have the feeling this is going to be a threading problem , but I'm not sure and if it is, I still don't know how to do that with swing)

I assume notify calls update() method. Since update() method changes the contents of textfield, make sure it is called in EDT ( Event Dispatch Thread). — avis, Oct 26 '13 at 07:06

score 3 · Accepted Answer · edited May 23 '17 at 10:27

3

Instead of looping through your observers explicitly, let Observable do it, as shown here.

this.setChanged();
this.notifyObservers();

Also, verify that you are not blocking the event dispatch thread. If so, consider using SwingWorker, which greatly simplifies Swing threading.

edited May 23 '17 at 10:27

Community

1
1

answered Oct 26 '13 at 07:44

trashgod

203,806
29
246
1,045

1

Thank you, I have used SwingWorker and once I had figured out how to get that working with my pattern mess it worked like a charm! – Dylan Meeus Oct 27 '13 at 01:59

Java Swing GUI freezes - observer pattern

1 Answers1