Question

I currently have a JFrame where on it’s content pane I draw images on from a game loop at 60 frames per second. This works fine, but at the right side, I now have more Swing elements on which I want to display some info on when selecting certain parts of the content pane. That part is a static GUI and does not make use of a game loop.

I’m updating it this way:

public class InfoPanel extends JPanel implements Runnable {
    private String titelType = "type: ";
    private String type;
    private JLabel typeLabel;
    private ImageIcon icon;

    public void update() {
        if (this.icon != null)
            this.typeLabel.setIcon(this.icon);

        if(this.type != null || this.type != "")
            this.typeLabel.setText(this.titelType + this.type);
        else
            this.typeLabel.setText("");
    }

    public void run() {
        try {
            Thread.sleep(150);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        this.update();
    }

(this method is only called when the player has actually moved, so it’s just called once – not 60 times per second)

I noticed that, when calling this update()-method from the game loop, I get flickering effects. I assume this is because updating the UI takes some time, so I decided to put it in a new thread. This reduced the flickering, but didn’t solve it.

Next, I decided to give the new thread low priority as the part of the screen which is redrawed 60 times a second is far more important. This reduced the flickering again, but it still happened. Then, I decided to use Thread.sleep(150); in the new thread before calling the update()-method, which solved the flickering effect on my system completely.

However, when running it on other systems, it still happens. Not as often as before (maybe one time per 20 seconds), but it’s still pretty annoying. Apparantly, just updating the UI in another thread doesn’t solve the problem.

Any ideas how to completely eleminate the flickering?

Answer 1

Call the update() in SwingUtilities.invokeAndWait() which stops the thread and updates UI in EDT.