SwingWorker background task pause

[madroadbiker]

I have successfully implemented a swingWorker to process a very long task in the background in my GUI. I have a button that allows the user to abort the process while it is running and that works fine. However, I would also like to add a button for the user to be able to temporarily suspend the background task and then continue. When I do that, the task gets suspended forever in the "while (pauseProcessing || abortProcessing)" loop and cannot be restarted again. Here is how I implemented it:

// The SwingWorker class
private class ProcessFile extends SwingWorker<Boolean, Void> {
    @Override
    public Boolean doInBackground() {
       return processFileList();
    }

    @Override
    protected void done() {
        try {
            if (this.get())
                statusBar.setText("done");
            else statuBar.setText("error");
        } catch (Exception e) {
            statusBar.setText("error while processing");
        }
    }
}

// The background task
private boolean processFileList() {
        for (int i = 0; i < numofFiles; ++i)
        {
            while (pauseProcessing || abortProcessing)
            {
                if (abortProcessing)
                {
                    errCode = errorCodes.errProcessAborted;
                    return false;
                }
            }
            lots more processing here...
        }
        return true;
}

// Button listeners
private void abortButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            
    if (dirList != null)
        abortProcessing = true;
}                                           

private void pauseButtonActionPerformed(java.awt.event.ActionEvent evt) {
    pauseProcessing = !pauseProcessing;
}

If this method for temporarily suspending the background task is incorrect, what is the correct method?

[Fubarable]

<Sorry -- never mind previous post: bad advice!>

Better advice: create an SSCCE.

[madroadbiker]

I'm not sure I understand. Can you show me?

[Fubarable]

Does your pause while loop have a short Thread.sleep in it? It should else it will tie up your app. Found this out in my SSCCE:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class SimplePauseProcessing extends JPanel {
   private static final int INDEX_MAX = 100;
   private static final long SLEEP_DELAY = 500;
   private JButton startProcessingBtn = new JButton("Start");
   private JToggleButton pauseProcessingBtn = new JToggleButton("Pause");
   private JButton endProcessingBtn = new JButton("End");
   private boolean abortProcessing;
   private boolean pauseProcessing;
   private MySwingWorker mySwingWorker;

   public SimplePauseProcessing() {
      add(startProcessingBtn);
      add(pauseProcessingBtn);
      add(endProcessingBtn);

      pauseProcessingBtn.setEnabled(false);
      endProcessingBtn.setEnabled(false);

      startProcessingBtn.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            startProcessingActionPerformed();
         }
      });
      endProcessingBtn.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            endProcessingActionPerformed();
         }
      });
      pauseProcessingBtn.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            pauseProcessingActionPerformed();
         }
      });
   }

   private void startProcessingActionPerformed() {
      abortProcessing = false;
      pauseProcessing = false;
      
      new MySwingWorker().execute();
      startProcessingBtn.setEnabled(false);
      endProcessingBtn.setEnabled(true);
      pauseProcessingBtn.setEnabled(true);
      pauseProcessingBtn.setSelected(false);
   }

   private void endProcessingActionPerformed() {
      abortProcessing = true;

      startProcessingBtn.setEnabled(true);
      endProcessingBtn.setEnabled(false);
      pauseProcessingBtn.setEnabled(false);
      pauseProcessingBtn.setSelected(false);
   }

   private void pauseProcessingActionPerformed() {
      pauseProcessing = pauseProcessingBtn.isSelected();
   }
   
   public boolean backGroundTask() {
      for (int i = 0; i < INDEX_MAX; i++) {
         System.out.println("Index: " + i);
         try {
            Thread.sleep(SLEEP_DELAY);
         } catch (InterruptedException e) {}
         
         if (abortProcessing) {
            return false;
         }
         
         while (pauseProcessing) {
            try {
               Thread.sleep(50);  // [color="red"]***** need this !!! *****[/color]
               if (abortProcessing) {
                  return false;
               }
            } catch (InterruptedException e) {}
         }
      }
      return true;
   }
   
   private class MySwingWorker extends SwingWorker<Boolean, Void> {

      @Override
      protected Boolean doInBackground() throws Exception {
         return backGroundTask();
      }
      
      @Override
      protected void done() {
         startProcessingBtn.setEnabled(true);
         pauseProcessingBtn.setEnabled(false);
         endProcessingBtn.setEnabled(false);
      }
      
   }

   private static void createAndShowUI() {
      JFrame frame = new JFrame("SimplePauseProcessing");
      frame.getContentPane().add(new SimplePauseProcessing());
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}

[madroadbiker]

Ah did not think of that! That worked! Thanks a heap!

[Fubarable]

Ah did not think of that! That worked! Thanks a heap!

Glad it helped, and you're welcome!