How to create a modal JDialog on top of another modal JDialog

Question

I have a modal settings dialog which is a JDialog. In this settings window I placed some components including a button to yet another modal settings dialog which is also a JDialog. I made them JDialogs because that is the only way I know of to make a modal dialog.

The problem is this: when I create the main settings dialog I have to construct the JDialog either without a parent Frame or with a parent Frame. Since my main window is a JFrame, I can just pass that to the main settings dialog constructor. But when I want to create the second modal settings dialog which should have the main settings dialog as a parent, I can't find a way to get the (J)Frame of the JDialog. I do want to pass that main settings dialog as a parent so that the second settings dialog centers on it when it is shown. Let's assume the second settings dialog has no constructor for passing a location, just the constructors of the JDialog.

Is there a way to get the (J)Frame of a JDialog? Is there a design flaw in my setup and should I have used something else for these settings dialogs? (And if so, how should I make these alternative settings dialogs modal?)

Thank you for your help, Erik

UPDATE: Thank you all for your answers. They led me to understand that apparently it's not absolutely necessary to have an owner for a JDialog. I thought this was needed for the dialog to be able to disable the owner until the dialog is closed, but apparently the modality is independent of the owner. I also noticed that even with an owner the dialog still doesn't center on the owner, so now my code is like:

public class CustomDialog extends JDialog {
    public CustomDialog(String title) {
        setModal(true);
        setResizable(false);
        setTitle(title);

        buildGUI();
    }

    public Result showDialog(Window parent) {
        setLocationRelativeTo(parent);
        setVisible(true);
        return getResult();
    }
}

This also allows for modal dialogs in modal dialogs.

Thanks for all your help!

Answer 1

Not sure what exactly you have as a problem, but here is an example on how you can have multiple modal dialogs:

import java.awt.BorderLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class TestDialog {

    protected static void initUI() {
        JPanel pane = newPane("Label in frame");
        JFrame frame = new JFrame("Title");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(pane);
        frame.pack();
        frame.setVisible(true);

    }

    public static JPanel newPane(String labelText) {
        JPanel pane = new JPanel(new BorderLayout());
        pane.add(newLabel(labelText));
        pane.add(newButton("Open dialog"), BorderLayout.SOUTH);
        return pane;
    }

    private static JButton newButton(String label) {
        final JButton button = new JButton(label);
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                Window parentWindow = SwingUtilities.windowForComponent(button);
                JDialog dialog = new JDialog(parentWindow);
                dialog.setLocationRelativeTo(button);
                dialog.setModal(true);
                dialog.add(newPane("Label in dialog"));
                dialog.pack();
                dialog.setVisible(true);
            }
        });
        return button;
    }

    private static JLabel newLabel(String label) {
        JLabel l = new JLabel(label);
        l.setFont(l.getFont().deriveFont(24.0f));
        return l;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                initUI();
            }
        });
    }
}