Opening JDialog with SwingWorker?

I have a project J2SE that use JPA. In some JDialogs I do returns getResultList() and populate JTable, JComboBox, JList etc. at constructor of class.

So when I will create any instance for these dialogs sometimes are slow.

I think use SwingWorker and JProgressbar and create a (loading) to open JDialogs is a good solution, but I don't know how to do this.

I'm trying this.

//
JProgressbar progress = new JProgressBar();

//custommer dialog
JDialog custommer = new JDialog(); //here slow because I have List<Customer> and others lists
custommer.setModal(true);

private void openDialogs(JDialog dialog){
    progress.setVisible(true);
    progress.setIndeterminate(true);

    SwingWorker sw = new SwingWorker(){
        protected Object doInBackground(){
          //opening dialog
          dialog.setVisible(true);
          return null;
        }
    }

    //after opened
    protected void done(){
        progress.setVisible(false);
    }

}

How to I can open JDialog and create a loading to open with SwingWorker and JProgressbar ?

Here comes the tricky bit, you need to get the SwingWorker started BEFORE you show the JDialog, but you also need to get the dialog visible in such away as not block other aspects of you code.

This example uses a PropertyChangeListener attached to the SwingWorker to monitor for the STARTED state, at which time it sets the progress dialog visible, but it does so using SwingUtilities.invokeLater, so as not to block the current event execution process...

It then uses the SwingWorker's done method to close the dialog when it's completed...

import java.awt.EventQueue;
import java.awt.Frame;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;

public class LongWaiting {

    public static void main(String[] args) {
        new LongWaiting();
    }

    public LongWaiting() {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {

                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }
                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new JLabel("Loading stuff"));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);

                Loader loader = new Loader(frame);
                loader.execute();

            }

        });
    }

    public class Loader extends SwingWorker {

        private ProgressPane progressPane;
        private JDialog dialog;

        public Loader(Frame owner) {
            progressPane = new ProgressPane();
            progressPane.setBorder(new EmptyBorder(5, 5, 5, 5));
            dialog = new JDialog(owner, "Loading", true);
            dialog.add(progressPane);
            dialog.pack();
            dialog.setLocationRelativeTo(owner);
            dialog.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
            addPropertyChangeListener(new PropertyChangeListener() {
                @Override
                public void propertyChange(PropertyChangeEvent evt) {
                    if ("state".equals(evt.getPropertyName())) {
                        if (getState() == StateValue.STARTED) {
                            SwingUtilities.invokeLater(new Runnable() {
                                @Override
                                public void run() {
                                    if (getState() == StateValue.STARTED) {
                                        dialog.setVisible(true);
                                    }
                                }
                            });
                        } 
                    } 
                }
            });
        }

        @Override
        protected Object doInBackground() throws Exception {
            Thread.sleep(10000);
            return null;
        }

        @Override
        protected void done() {
            dialog.dispose();
        }

    }

    public class ProgressPane extends JPanel {

        private JLabel message;
        private JProgressBar pb;

        public ProgressPane() {
            message = new JLabel("Loading...");
            pb = new JProgressBar();
            pb.setIndeterminate(true);

            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            gbc.weightx = 1;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            gbc.insets = new Insets(2, 0, 2, 0);
            add(message, gbc);
            add(pb, gbc);
        }

    }

}