Tuesday, February 14, 2012

updated gui application

I need to write an application that will check for something every X time and update it to GUI comtols. I have some little knowledge in java and written some applications before but I've never dealt with stuff like multiple threads and updating the GUI.

I though it will be an easy task so I've started to write my software. Everything else is pretty much functioning. I just cant get the app to perform checks every X time and then update the GUI.

Can someone please give some guidance on this? What shold I look into? what is the common practice? Is it threads? recursive? anything else?

Also if possible provide me some code examples, I can understand better.

thanks for any effort!


  1. I'm assuming you're using Swing. If so, use a Swing Timer.

    Or, if the check itself is some long-running task that must not be done in the GUI thread (because it would freeze it), then use a SwingWorker and submit it to a ScheduledExecutorService created by the Executors class.

  2. Try something like:

    private volatile boolean killCheck;

    public void startChecking() {
    killCheck = false;
    Thread checker = new Thread() {
    public void run() {
    for (;;) {
    try { Thread.sleep( 500 ); }
    catch (InterruptedException ie) { break; }
    if (killCheck) break;
    EventQueue.invokeLater( new Runnable() {
    public void run() {
    // Update GUI here on EventQueue.
    } );

    public void stopChecking() { killCheck = true; }

    Timers (and there are at least two, in swing and util) are lots of fun and elegant, but sometimes you just need to get the job done. Replace my 500 with your "X time". Make sure to make Swing calls on the EventQueue! And maybe add a message if the InterruptedException gets thrown.

    Check out a SwingWorker; it will do the same thing with more safety, but if you're going to be doing a lot of this you might find there's more power in doing it yourself.