SwingWorker

[3.14.TR]

Hi,
I´m not sure, if I have chosen the right topic for my problem, nontheless I hope that I have.

I´d like to create a simple progressBar app, involving simple delayed counter and progressbar-dialog.

My vision is simple: with 500ms delay counting untill 10 is being displayed to the console.
Meanwhile, the indeterminete progressbar is being displayed.
After counting is done, I´d like to return the integer of value 987 (this is very important for me, in order to develop app later)

According to some tutorials I tried to code this app, but unfortunatelly unsuccessfully.

Here is my code:

public class Task{
  public static void main(String[] args) {
    final JProgressBar progressBar = new JProgressBar(0, 10);

    final CounterTask task = new CounterTask();

    JButton startButton = new JButton("Start");
    startButton.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        System.out.println("start");
        task.execute();
        
        Integer res=new Integer(5);
        try{
          System.out.println("try");
          while(!task.isDone()){
            System.out.println("while");
            res=task.get(50, TimeUnit.MILLISECONDS);
            System.out.println("res: "+res);
            System.out.println("afterRes");
          } 
          res=task.get(50, TimeUnit.MILLISECONDS);
            System.out.println("res: "+res);
            
          System.out.println("/while"); 
        }
        catch (Exception ex){}
      }
      
    });



    JPanel buttonPanel = new JPanel();
    buttonPanel.add(startButton);


    JPanel cp = new JPanel();
    LayoutManager layout = new BoxLayout(cp, BoxLayout.Y_AXIS);
    cp.setLayout(layout);
    cp.add(buttonPanel);
    cp.add(progressBar);

    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setContentPane(cp);
    frame.pack();
    frame.setVisible(true);
  }
}

class CounterTask extends SwingWorker<Integer, Integer> {
  
  protected JDialog dialog;
  
  @Override
  protected Integer doInBackground() throws Exception {
    int i = 0;
    int count = 10;
    
    dialog=new JDialog();
    JProgressBar progressBar=new JProgressBar();
    progressBar.setIndeterminate(true);
    dialog.add(progressBar);
    dialog.pack();
    dialog.setVisible(true);
    
     
    while (!isCancelled() && i < count) {
      i++;
      Thread.sleep(500);
      System.out.println(i);
    }
    publish(new Integer(987));
    return new Integer(987);
  }   

  @Override
  protected void done() {
    dialog.setVisible(false);  
    System.out.println("Done !");
  }
}

The counting is ok as same as progressbar, however the return value hasn´t been written.

Please, could anybody help me find out, where my problem is, or furthermore could anybody provide me with working solution?

Thank you very much

[Fubarable]

One problem with your code is this:

                    while (!task.isDone()) {
                        System.out.println("while");
                        res = task.get(50, TimeUnit.MILLISECONDS);
                        System.out.println("res: " + res);
                        System.out.println("afterRes");
                    }

As this could freeze the event dispatch thread, the main Swing thread, and nullify all the benefits of using a SwingWorker. But there is a better way since SwingWorkers have built in support for a PropertyChangeListener, and you might want to use that to your advantage. With this, you could even use a determinate progress bar rather than an indeterminate progress bar. For example,

import java.awt.Dialog.ModalityType;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.List;

import javax.swing.*;
import javax.swing.SwingWorker.StateValue;

@SuppressWarnings("serial")
public class Task3 extends JPanel {
    private static final int FINAL_VALUE = 987;
    private JTextArea textArea = new JTextArea(10, 20);
    private JButton startBtn = new JButton("Start");
    
    public Task3() {
        JPanel startBtnPanel = new JPanel();
        startBtnPanel.add(startBtn);
        startBtn.addActionListener(new ActionListener() {
            
            public void actionPerformed(ActionEvent e) {
                startBtnActionPerformed();
            }
        });
        
        textArea.setEditable(false);
        textArea.setFocusable(false);
        setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));
        add(new JScrollPane(textArea, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, 
                JScrollPane.HORIZONTAL_SCROLLBAR_NEVER));
        add(startBtnPanel);
    }
    
    private void startBtnActionPerformed() {
        startBtn.setEnabled(false);
        Window win = SwingUtilities.getWindowAncestor(this);
        final JDialog dialog = new JDialog(win, "Progress", ModalityType.APPLICATION_MODAL);
        final JProgressBar progressBar = new JProgressBar();
        JPanel progressPanel = new JPanel();
        progressPanel.add(progressBar);
        progressPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        dialog.getContentPane().add(progressPanel);
        dialog.pack();
        dialog.setLocationRelativeTo(null);
        final CounterTask3 counterTask3 = new CounterTask3(this, FINAL_VALUE);
        counterTask3.addPropertyChangeListener(new PropertyChangeListener() {
            
            public void propertyChange(PropertyChangeEvent evt) {
                if (evt.getPropertyName().equals("state")) {
                    if (counterTask3.getState().equals(StateValue.DONE)) {
                        dialog.setVisible(false);
                        startBtn.setEnabled(true);
                        // could call counterTask3.get() here to get the final value
                    }
                } 
                else if (evt.getPropertyName().equals("progress")) {
                    int progress = counterTask3.getProgress();
                    progressBar.setValue(progress);
                }
            }
        });
        counterTask3.execute();
        dialog.setVisible(true);
    }

    public void appendToTextArea(String text) {
        textArea.append(text);
    }
    
    public static void main(String[] args) {
        
        
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createGui();
            }
        });
    }

    private static void createGui() {
        Task3 task3 = new Task3();
        JFrame frame = new JFrame("App");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(task3);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

class CounterTask3 extends SwingWorker<Integer, Integer> {
    private static final int MAX_COUNTER = 10;
    private static final long SLEEP_TIME = 500;
    private Task3 task3;
    private int finalValue;

    public CounterTask3(Task3 task3, int finalValue) {
        this.task3 = task3;
        this.finalValue = finalValue;
    }

    @Override
    protected Integer doInBackground() throws Exception {
        int counter = 0; 
        while (counter < MAX_COUNTER && !isCancelled()) {
            counter++;
            Thread.sleep(SLEEP_TIME);
            publish(counter);
            setProgress((counter * 100)/MAX_COUNTER); // if use determinate PB 
        }
        return finalValue;
    }
    
    @Override
    protected void process(List<Integer> chunks) {
        for (Integer intChunk : chunks) {
            task3.appendToTextArea("int value: " + intChunk + "\n");
        }
    }
    
    @Override
    protected void done() {
        task3.appendToTextArea("Final value: " + finalValue + "\n");
    }
    
}

There are several ways to skin this cat and my suggestion is not the only way, and may not even be the best way.

[3.14.TR]

hi,
thank you very much for help.
The property-change listener works good, the determinate progressBar is not nessesary, anyway thanks a lot.

Nontheless, I probably have expresed in a strange way (sorry for my english) - I want to get the Integer (987) from worker into the rest of my other code, i.e. write returned int from propertyChangeListener insteand of from done() method.

I asked you to explain me the example with only integer, but in future I´m going to let it return more complicated classes, e.g. ResultSet etc.

Thank you very much for your helpful responses.

[3.14.TR]

oh man,
I´m so sorry, I didn´t see your coment. It works fine. Thanks for help