Question

I have a GUI in which some groups of JComponents get “batch-updated”, i.e., I have a loop and for almost every iteration of the loop, I need to update these JComponents. So, I tried to do the updates alongside the computations in the loop but it didn’t go well being that, (if I interpret correctly) the updates were “slowed down” by the computations, the effect being only the last update became perceptible to the user.

That’s when I thought of putting all update-related code on a separate thread. First off, I created an interface called UpdatableComponent which will wrap all JComponents that must be updated:

public interface UpdatableComponent {
/**
 * Implementors should be the one responsible for typecasting update
 * into the appropriate objects.
 */
public void update(Object update);
}

So if, for instance, I want to update a JLabel

public class UpdatableJLabel implements UpdatableComponent{
    private JLabel l;

    public UpdatableJLabel(JLabel l){
        this.l = l;
    }

    public void update(Object update){
         l.setText((String) update);
    }
}

Then, my Runnable class for threading:

public class UIUpdateRunnable implements Runnable {

private UpdatableComponent[] forUpdating;

public UIUpdateRunnable(UpdatableComponent[] uc) {
    forUpdating = uc;
}

public void run() {
    int limit = forUpdating.length;

    for(int i = 0; i < limit; i++){

    }
}

}

And this is where I hit a snag. How do I know what argument to pass for each UpdatableComponent’s update method? I thought of maintaining an Object array, arguments, which will map an UpdatableComponent to an argument for its update method (I have a setter method for it, of course). But then that would be (1) too tightly-coupled—bad design!—and (2) too much for a thread; the loop inside run will continuously call update on each UpdatableComponent, giving it its designated argument, updating regardless whether it actually updated or not.

I can’t help but feel that I may have missed a simple way to do it. Any suggestion/advice will be very welcome. Thank you.

Answer 1

It sound like a SwingWorker is what you are looking for. The computation is done inside the method doInBackground(), results are publish()ed and process() then updates the components.