Question

            int r = JOptionPane.showOptionDialog(null, 
                    myPanel, 
                    "Choose", 
                    JOptionPane.NO_OPTION,
                    JOptionPane.PLAIN_MESSAGE, 
                    null, 
                    new String[]{}, // this is the array
                    "default");

How do you catch the event when the user has clicked the X to close the dialog?

Answer 1

From the documentation:

When one of the showXxxDialog methods returns an integer, the possible
values are:

YES_OPTION
NO_OPTION
CANCEL_OPTION
OK_OPTION
CLOSED_OPTION

I believe you are looking for the CLOSED_OPTION one.