windowClosed多次触发。 这是错误还是功能？

Question

Take the following code:

import java.awt.Dialog;
import java.awt.event.ActionEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;

public class WeirdDialogShitTest implements Runnable {
    private JFrame frame;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new WeirdDialogShitTest());
    }

    @Override
    public void run() {
        frame = new JFrame("Test");
        frame.add(new JButton(new AbstractAction("Show Dialog") {
            @Override
            public void actionPerformed(ActionEvent event) {
                showDialog();
            }
        }));
        frame.pack();
        frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
        frame.setVisible(true);
    }

    private void showDialog() {
        JDialog dialog = new JDialog(frame, "Dialog", Dialog.ModalityType.DOCUMENT_MODAL);
        dialog.add(new JLabel("Content here"));
        dialog.pack();
        dialog.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
        dialog.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosed(WindowEvent event) {
                JOptionPane.showMessageDialog(frame, "windowClosed fired");
            }
        });
        dialog.setVisible(true);
    }
}

I expect windowClosed to be called once - when the dialog closes.

What actually happens is that it is called twice - once when the dialog closes, and once when the containing frame closes.

When I traced it to see what was going on, here's what I found:

• When dispose() is called on the parent, it disposes all children too. Fair enough.
• All child dialogs remain in the list of children despite no longer existing. This seems dodgy to me. (Are they ever removed?)
• dispose() unconditionally fires windowClosed whether the window is already disposed or not. This seems dodgy to me also.

The end result is getting windowClosed once for the dialog itself and once for each ancestor. :/

But maybe this is the intended behaviour?

Answer 1

Should use frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); on main frame. This will solve your problem. Try:

public class WeirdDialogShitTest implements Runnable {
    private JFrame frame;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new WeirdDialogShitTest());
    }

    @Override
    public void run() {
        frame = new JFrame("Test");
        frame.add(new JButton(new AbstractAction("Show Dialog") {
            @Override
            public void actionPerformed(ActionEvent event) {
                showDialog();
            }
        }));
        frame.pack();

        frame.setVisible(true);
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        //Use EXIT_ON_CLOSE here.
    }

    private void showDialog() {
        JDialog dialog = new JDialog(frame, "Dialog", Dialog.ModalityType.DOCUMENT_MODAL);
        dialog.add(new JLabel("Content here"));
        dialog.pack();
        dialog.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
        dialog.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosed(WindowEvent event) {
                JOptionPane.showMessageDialog(frame, "windowClosed fired");

            }
        });
        dialog.setVisible(true);
    }
}