How to update java GUI from Thread?

Question

 private void StartActionPerformed(java.awt.event.ActionEvent evt) {

        Queue queue=new Queue();
        int target=Integer.parseInt(Target.getText());
        String path=Path.getText();
        final Producer p=new Producer(queue, target);
        Consumer c=new Consumer(queue);
        p.start();
        c.start();

        while(p.finish !=true)
        {
          Runnable r = new Runnable() {
            public void run() {
              ProgressPrecent.setValue(Producer.ProgressPercent);
            }
          };
          if(EventQueue.isDispatchThread()) {
            r.run();
          }
          else {
            EventQueue.invokeLater(r);
          }
       }
 }

I have two classes that have a shared Queue. one of them is Producer that produces till a target other one consume those elements. all of two extends Thread. I want to display the progress percent to the user, but it freeze my GUI so what should I do?

Well, you will have to be more specific if you need help. You might also want to improve your question to explain your code. Reading the FAQ will help you. — devsnd, Nov 24 '12 at 17:05
@sarcan: Not everybody speaks/writes english as their mothertongue. You should not discriminate someone because of language, since it isn't the actual problem. It's about explaining what has been tried etc... — devsnd, Nov 24 '12 at 17:07
I had this problem in C# but it solve, you can see the question here http://stackoverflow.com/questions/13141280/updating-progress-bar-from-thread-in-c-sharp — Alyafey, Nov 24 '12 at 17:14
Several useful examples are cited in the [answers to this question](http://stackoverflow.com/q/13538275/230513). — trashgod, Nov 24 '12 at 18:20

morja · Answer 1 · 2012-11-24T18:32:32.610

6

I think you will have to put the whole while loop into a thread. Otherwise the loop will block your ActionEvent and thus freezes the UI.

Something like:

new Thread(){
    public void run(){
        while(!p.finish){
           SwingUtilities.invokeLater(new Runnable(){
             public void run(){
               ProgressPrecent.setValue(Producer.ProgressPercent);
             }
           }); 
           try{
              Thread.sleep(100);
           }catch(...){}
        }
    }
}.start();

edited Nov 24 '12 at 18:32

answered Nov 24 '12 at 17:57

morja

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How will you synchronize access to `ProgressPrecent`? – trashgod Nov 24 '12 at 18:21
Just tried to point out that the loop will cause the initial event to block. Updated my answer. – morja Nov 24 '12 at 18:36
Without knowing otherwise, it would be dangerous to call `ProgressPrecent.setValue` - All UI updates MUST be executed within the Event Dispatching Thread - While in theory your answer is correct, is misleading and will end in "why do I get paint artifices" questions, followed "but I was told to" answers ... – MadProgrammer Nov 24 '12 at 20:39

score 6 · Answer 2 · edited May 23 '17 at 11:47

Worker Threads by default never to invoked EventDispatchThread, you have issue with Concurency in Swing
all updates to Swing GUI must be done on EDT
Runnable could be proper way but ProgressPrecent.setValue(Producer.ProgressPercent); must be wrapped in invokeLater

code

SwingUtilities.invokeLater(new Runnable(){
    public void run(){
        ProgressPrecent.setValue(Producer.ProgressPercent);
    }
});

remove testing for EDT,

code lines

if(EventQueue.isDispatchThread()) {
   r.run();
}

Workers Thread by defaut never ever to invoke EDT, then doesn't matter if is started from EDT, nor tested for isDispatchThread() doesn't make me some sence

never ever, don't to use Thread.sleep(int) inside Swing Listeners, because caused freeze Swing GUI too
I think you can to use SwingWorker for this job too

How to update java GUI from Thread?

2 Answers2

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