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If you were trying out the above Java programs, and were particularly
observant while you ran the programs, you may have noticed a peculiarity when
you tried to close the frame (i.e., clicked on the 'x' on the right side of the
title bar, or clicked on the icon on the left side of the title bar, and
selected Close on the resulting menu).
When you close the frame, it becomes invisible, but the program is still
running! Why is this?
It turns out that you can choose what a JFrame should do when you close
it. The choices are:
| Constant |
Defined |
Description |
DO_NOTHING_ON_CLOSE |
javax.swing.WindowConstants |
Don't do anything; require the program to handle the operation in the windowClosing
method of a registered WindowListener object. |
HIDE_ON_CLOSE
(the default) |
javax.swing.WindowConstants |
Automatically hide the frame after invoking any registered WindowListener
objects. |
DISPOSE_ON_CLOSE |
javax.swing.WindowConstants |
Automatically hide and dispose the frame after invoking any registered WindowListener
objects. |
EXIT_ON_CLOSE |
javax.swing.JFrame
and
javax.swing.WindowConstants |
Exit the
application using the System.exit method. Use this
only in applications. |
For the moment, don't worry about those references to windowClosing method
and WindowListener objects. We'll get to those when we talk about Java
events.
So, to specify that closing the frame should also exit the program, you have
to specify it explicitly:
package swingExamples;
import javax.swing.JFrame;
public class ExitingFrame extends JFrame
{
public ExitingFrame()
{
setTitle("ExitingFrame");
setBounds(100, 200, 300, 200);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
public static void main(String[] args)
{
ExitingFrame frame = new ExitingFrame();
frame.setVisible(true);
}
}
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which produces this equally stunning result:
But at least you can tell it to exit! |
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