Re: Pressing ALT obscures components when using Windows L&F

"Andrew Thompson" <u32984@uwe>
Wed, 11 Apr 2007 02:40:41 GMT
ub wrote:

I have a JFrame that displays a big JLabel in the background and a
JCheckBox in the front.

The JCB is actually 'above' the JL, here.

When using the Windows L&F and I press the Alt-key the JLabel is
repainted but not the JCheckBox in front of it. As a consequence the
checkbox disappears. Forcing a repaint (e.g. by resizing the frame)
will make the checkbox re-appear.

When not using the Window L&F everything is fine.

I did not see the stated problem, either way, but
noticed the very fragile code being used.

Any suggestion how to work around this problem?

Use layouts. This might not be exactly what you
want, it might require a nested layout to get the
full effect, but it is perhaps a starting point..

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.UnsupportedLookAndFeelException;

public class AltKeyRepaint {
    public static void main(String args[]) throws ClassNotFoundException,
            InstantiationException, IllegalAccessException,
            UnsupportedLookAndFeelException {
        // Use the System (i.e. "Windows") L&F
        // ie only if the user is Window'd
        // otherwise it will be the Mac. or *nix style PLAF's

        // The frame to display the sample
        JFrame frame = new JFrame("Frame");

        // this is probably not only the source of the
        // current problems, but a dozen others that
        // have either not been seen, or not manifested yet.
        // Do not use 'null' layouts unless you..
        // a) know what your doing, (and potentially also..)
        // b) are designing a custom layout,
        // frame.getContentPane().setLayout(null);
        JPanel p = new JPanel(new BorderLayout());

        // A big colored label in the background
        JLabel label = new JLabel("A sample label in the CENTER",
        // play with the padding numbers,
        // to get the right effect..
        label.setBorder( new EmptyBorder(30,15,50,15) );

        // A check box on top of the background label
        JCheckBox chkBox = new JCheckBox("a check box in NORTH");
        chkBox.setBorder( new EmptyBorder(20,5,20,5) );

        // Add the label and check box to the frame
        p.add(chkBox, BorderLayout.NORTH);
        p.add(label, BorderLayout.CENTER);


        // display it
        // deprecated in Java 1.2/1.5

        // this cause everything to become the
        // preferred size, which might be different
        // on different platforms, PLAF's, font sizes,
        // Java versions, or screen resolutions.


Andrew Thompson

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