How to pass SwingWorker to other methods

Question

My “problem” can be described as follows. Suppose we have an intensive process that we want to run in the background and update its Swing JProgress panel. The solution is easy:

import java.util.List;

import javax.swing.JOptionPane;
import javax.swing.JProgressBar;
import javax.swing.SwingWorker;


/**
 * @author Savvas Dalkitsis
 */
public class Test {

    public static void main(String[] args) {
        final JProgressBar progressBar = new JProgressBar(0,99);
        SwingWorker<Void, Integer> w = new SwingWorker<Void, Integer>(){

            @Override
            protected void process(List<Integer> chunks) {
                progressBar.setValue(chunks.get(chunks.size()-1));
            }

            @Override
            protected Void doInBackground() throws Exception {

                for (int i=0;i<100;i++) {
                    publish(i);
                    Thread.sleep(300);
                }

                return null;
            }

        };
        w.execute();
        JOptionPane.showOptionDialog(null,
                new Object[] { "Process", progressBar }, "Process",
                JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE,
                null, null, null);
    }

}

Now suppose I have various methods that take a lot of time. For example, we have a method that downloads a file from the server. Or another that is uploaded to the server. Or something really. What is the proper way to delegate a publishing method to such methods so that they can update the GUI accordingly?

What I have found so far is this (suppose the "aMethod" method is in some other package, for example):

import java.awt.event.ActionEvent;
import java.util.List;

import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JOptionPane;
import javax.swing.JProgressBar;
import javax.swing.SwingWorker;


/**
 * @author Savvas Dalkitsis
 */
public class Test {

    public static void main(String[] args) {
        final JProgressBar progressBar = new JProgressBar(0,99);
        SwingWorker<Void, Integer> w = new SwingWorker<Void, Integer>(){

            @Override
            protected void process(List<Integer> chunks) {
                progressBar.setValue(chunks.get(chunks.size()-1));
            }

            @SuppressWarnings("serial")
            @Override
            protected Void doInBackground() throws Exception {

                aMethod(new AbstractAction() {

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        publish((Integer)getValue("progress"));
                    }
                });

                return null;
            }

        };
        w.execute();
        JOptionPane.showOptionDialog(null,
                new Object[] { "Process", progressBar }, "Process",
                JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE,
                null, null, null);
    }

    public static void aMethod (Action action) {
        for (int i=0;i<100;i++) {
            action.putValue("progress", i);
            action.actionPerformed(null);
            try {
                Thread.sleep(300);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

}

It works, but I know something is missing for him. Any thoughts?

Answer 1

( , )

, , , . Java PropertyChangeSupport . .

-, . "" () , GUI . :

/**
 * Wrapper for the background logic.
 *
 * <T> return type
 * <S> intermediary type (the "shout out")
 */
public static abstract class LoudCall<T, S> implements Callable<T> {

    private PropertyChangeSupport pcs;
    private S shout;

    public LoudCall() {
        pcs = new PropertyChangeSupport(this);
    }

    public void shoutOut(S s) {
        pcs.firePropertyChange("shoutOut", this.shout, 
                this.shout = s);
    }

    public void addListener(PropertyChangeListener listener) {
        pcs.addPropertyChangeListener(listener);
    }

    public void removeListener(PropertyChangeListener listener) {
        pcs.removePropertyChangeListener(listener);
    }

    @Override
    public abstract T call() throws Exception;
}

/**
 * Wrapper for the GUI listener.
 *
 * <T> return type
 * <S> intermediary type (the "shout out" to listen for)
 */
public static abstract class ListenerTask<T, S> extends SwingWorker<T, S> 
        implements PropertyChangeListener {

    private LoudCall<T, S> aMethod;

    public ListenerTask(LoudCall<T, S> aMethod) {
        this.aMethod = aMethod;
    }

    @Override
    protected T doInBackground() throws Exception {
        aMethod.addListener(this);
        return aMethod.call();
    }

    @Override
    public void propertyChange(PropertyChangeEvent evt) {
        if ("shoutOut".equals(evt.getPropertyName())) {
            publish((S)evt.getNewValue());
        }
    }

    @Override
    protected abstract void process(List<S> chunks);
}

Swing. ProgressBar "" Integer, - Void:

public class ProgressExample {  
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
    @Override
    public void run() {

        // 1. setup the progress bar
        final JProgressBar progressBar = new JProgressBar(0, 99);

        // 2. Wrap the logic in a "Loud Call"
        LoudCall<Void, Integer> aMethod = new LoudCall<Void, Integer>() {
            @Override
            public Void call() throws Exception {
                for (int i = 0; i < 100; i++) {
                    // "i have an update for the GUI!"
                    shoutOut(i);
                    Thread.sleep(100);
                }
                return null;
            }
        };

        // 3. Run it with a "Listener Task"
        (new ListenerTask<Void, Integer>(aMethod) {
            @Override
            protected void process(List<Integer> chunks) {
                progressBar.setValue(chunks.get(chunks.size() - 1));
            }
        }).execute();

        // 4. show it off!
        JOptionPane.showOptionDialog(null,
            new Object[] { "Process", progressBar }, "Process",
            JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE,
            null, null, null
        );
    }
        });
    }
}

- GUI, (, "" ). , .

, , , , -!

Answer 2

, SwingWorker . SwingWorker .

SwingWorker doInBackground, . , EDT SwingWorker .

Answer 3

. , , , :

• , doInBackGround(). JProgressBar - SwingWorker, SwingWorker ( , )
• , , , , ( , ). , , (, ), . , ,
• , , fancy. , . , - , , JProgressBar. Thread, , ( ). JProgressBar . - , . .

In the third paragraph, I described how to execute Thread from a method that completes some task that is not iterative (at least not in our Java code) and cannot be interrupted. Updates to the JProgressBar thread that was set as a method parameter. This, however, is definitely slower than a pure method calling