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

"ub" <>
11 Apr 2007 05:30:53 -0700
The code I presented is the smallest code sample I could come up to
show the problem I ran into. Using the "null" layout was the simplest
way to demonstrate the issue. Actually a custom-made LayoutManager is
used in the real application but shows exactly the same behaviour as
the "null" layout.

The "real" application is part of an "AWT to Swing" porting project.
In that application the components are created dynamically, based on
some "form definitions" that define the location and size of the
individual components. Because of the amount and size of these
definitions (>8000, typically more than 10 components in each form)
rewriting the layout is not really an option.

I did some more tests and it looks like the issue also depends on the
graphic card. When using a DVI output the button disappears, but on a
VGA output everything is fine. So it may be a driver issue. Does that
makes sense?


On Apr 11, 4:40 am, "Andrew Thompson" <u32984@uwe> wrote:

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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