Trying to stop swingworker

Question

I have a custom JDialog that pops up when my SwingWorker thread fires up. The dialog just has a JProgressbar and a Button (cancel button). I am trying to figure out how to cancel my SwingWorker, but am having no luck. I think I am on the right path though. I wrote a cancel method, now I just need to figure out how to call it when the button is pushed. Code is below...

            btn_Cancel.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) 
                {
                   //trying to access cancel()
                }
             });

        SwingWorker worker = new SwingWorker<String, Void>() { 
        @Override
        protected String doInBackground() throws Exception {
                while (runLoad.getState() != Thread.State.TERMINATED &&      !isCancelled()) {
                    try {
                        synchronized (this) {
                            Thread.sleep(2000);
                        }
                    } catch (InterruptedException e){}
                }
                return null;
            }
        @Override
        public void done() {
                try {
                   get(); 
                } catch (InterruptedException | ExecutionException ex) {
                    JOptionPane.showMessageDialog(null,
                    "Somethings Wrong: " + ex.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
                }
              Progress.setVisible(false);
              Progress.dispose();
            }
        public void cancel(SwingWorker worker){
            worker.cancel(true);
         }
       };
       worker.execute();

score 1 · Accepted Answer · answered Dec 06 '13 at 17:31

1

Your cancel button should call the SwingWorker#cancel method

final SwingWorker worker = ...;

btn_Cancel.addActionListener(new ActionListener() {
  @Override
  public void actionPerformed(ActionEvent e) {
    worker.cancel( true );
  }
});

In your worker, you have to make sure to check the cancel flag

SwingWorker worker = new SwingWorker<String, Void>() { 
  @Override
  protected String doInBackground() throws Exception {
    while ( !isCancelled() ) {
      //do your stuff
    }
  }
}

Note that you need to create the worker before you create your ActionListener

answered Dec 06 '13 at 17:31

Robin

36,233
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This works! I have been beating my head on this for a week trying to get the cancel button to function correctly! Thank you. – yellowman Dec 06 '13 at 18:33
Afaik, you should never need to check `isCancelled()` inside `doInBackground()` because it will exit the background thread as soon as `cancel(true)` is called. You need check `isCancelled()` before calling `get()` to avoid an `InterruptedException` in the `done()` method. – ryvantage Dec 07 '13 at 18:11

score 0 · Answer 2 · answered Dec 06 '13 at 15:32

0

As explained in the official documentation, you need to check isCancelled() in your SwingWorker callback method.

answered Dec 06 '13 at 15:32

Domi

22,151
15
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score 0 · Answer 3 · answered Dec 06 '13 at 15:33

0

You could call

worker.cancel(true);

in your button action listener?

answered Dec 06 '13 at 15:33

Joe Birch

371
2
7

This was what I was initially trying, but when I add that to my ActionListener it says that it cannot find symbol worker. – yellowman Dec 06 '13 at 16:25

Keerthivasan · Answer 4 · 2013-12-06T17:49:55.977

0

You should call

worker.cancel(true); //this will set the cancel flag of the worker

Then, when you invoke isCancelled() this will return true. So, you Can check this state in your loop

edited Dec 06 '13 at 17:49

answered Dec 06 '13 at 15:40

Keerthivasan

12,760
2
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I added worker.cancel(true); to my listener and this seemed to work after I made my SwingWorker final. When I changed the condition of my while loop to be while(!worker.isCancelled()) I get an error that says that variable might not have been initialized. Any ideas? – yellowman Dec 06 '13 at 17:16
isCancelled() would be enough, since it is an anonymous class definition. Updated my answer as well. thanks – Keerthivasan Dec 06 '13 at 17:51

Trying to stop swingworker

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