Adding Joptionpane in shutdownHook

Question

Hi Is there any way to show joptionpane in shutdownhook i.e I need to show a confirmdailog in my shutdownhook event

Answer 1

If there is, it won't help you.

The shutdown hooks are invoked asynchronously as part of the JVM shutdown, so a "confirm" dialog won't really confirm anything as you can't halt or reverse the shutdown process.

Answer 2

It seems like you want some sort of prompt when the user finishes with the program but hasn't done some commit action (close a document with unsaved changes). If that is the case, I would put a WindowListener on the window whose closing should trigger the prompt and override windowClosing(WindowEvent e) {...} to show your JOptionPane. According to the JavaDocs you can override the windowClosing at this time. This gives you an opportunity to have a "save, discard, cancel" diaglog for documents with unsaved changes.

Answer 3

I suspect what you want is not a shutdown hook, but a "really quit?" JOptionPane. If so, here's an example of how to do it:

import javax.swing.*;
import java.awt.event.*;

public class ConfirmToCloseTest {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                final JFrame frame = new JFrame();
                frame.addWindowListener(new WindowAdapter() {
                    public void windowClosing(WindowEvent e) {
                        if (JOptionPane.showConfirmDialog(frame, "Really quit?", "", JOptionPane.YES_NO_OPTION) == JOptionPane.YES_OPTION) {
                            System.exit(0);
                        }
                    }
                });
                frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
                frame.getContentPane().add(new JLabel("Hello world"));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

}

Answer 4

A shutdown hook is supposed to execute quickly. Waiting for a user to make a decision is not the kind of action a shutdown hook is meant for. A shutdown hook in an interactive program does not make sense. The real use case for shutdown hooks is for releasing resources and other housekeeping when the JVM is terminated abnormally.