Question

I have problem with refreshing swing components inside Mouse action event handler. Problem is that all jLabels which are changed in this function that their changes are visible after jButton1MouseClicked() is done. Here is my function:

private void jButton1MouseClicked(java.awt.event.MouseEvent evt) {                                      

    int cycles = Integer.parseInt(c.settings.get("cycles"));
    statusMessageLabel.setText("Data collection in progress...");

    for(int i=1;i <= Integer.parseInt(c.settings.get("cycles"));i++) {

        jLabelCycle.setText(Integer.toString(i));

        //here are some functions which are implementing data collection


        if(i < cycles){
            int counter = Integer.parseInt(c.settings.get("interval"));
            while(counter >= 0){
                jLabelTimer.setText(Integer.toString(counter));
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException ex) {
                    Logger.getLogger(AppCView.class.getName()).log(Level.SEVERE, null, ex);
                }
                counter--;
            }
        }

    }
    statusMessageLabel.setText("Data collection has been finished.");
}    

Can you please help me ? I really need this changes to be visible immidiaetly because one jLabel visualize counting till next cycle and second one is visualizating actual cycle number. I tried call function repaint() on all jLabels after i changed them but it didnt help.

Thank you all for any help.

Answer 1

In AWT, much like most other GUI systems, all events including repaints are done on a single thread, the AWT Event Dispatch Thread (EDT). You are blocking that thread in the event listener, so the repaint events on the label cannot get through.

I suggest rewriting your code to use use javax.swing.Timer instead of Thread.sleep.

In general, long running operations should be handled on a separate thread. Any operations touching AWT or Swing components should be queued for running on the AWT EDT using java.awt.EventQueue.invokeLater.