I think I misunderstand the documentation for JLayeredPane

Hello. I'm trying to use a JlayeredPane in a small application and it isn't going well at all. So to try and find out about why it isn't working and how to make it work I made a very simple demo application that demonstrates my problem.

All the application does is make a 400x400 pixel JlayeredPane appear and then adds 8 NumberPanel objects to it, each on its own layer. The NumBerPanel object is simply a non-opaque JPanel that draws its number that it represents at the co-ordinate n + 1 x 30, n + 1 x30. Essentially drawing numbers 0 - 7 in a diagonal line from the top corner (before some layers are removed anyway). The problem is that any time I try to remove a layer, the wrong one is always removed. It is always the opposite layer that gets removed. So when the loop that removes layers begins and pane.remove(r); is called while r equals 7, it actually removes layer 0. When r equals 6 then layer 1 is removed and so on. Here's the code I have right now which includes a call to System.out.println(); in each loop that adds and removes the panels, so I could be sure no re-indexing of NumberPanels in layers was going on, and a call to JLayeredPane.setLayer() on line 24 which I noticed the documentationat Java Platform SE 7 said

Quote:

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Originally Posted by http://docs.oracle.com/javase/7/docs/api/index.html?javax/swing/JLayeredPane.html

The layer should be set before adding the child to the parent.

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But doesen't seem to make any difference at all in this example.

Code:

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package layeredpain;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;

public class LayeredPain extends JFrame {

    private final Dimension paneSize = new Dimension(400, 400);

    public LayeredPain() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setTitle("Layered Pain");
        JLayeredPane pane = new JLayeredPane();
        getContentPane().add(pane, BorderLayout.CENTER);
        pane.setPreferredSize(paneSize);
        for(int a = 0; a < 8; a++) {
            NumberPanel numPan = new NumberPanel(a, paneSize);
            pane.setLayer(numPan, a);
            pane.add(numPan, new Integer(a));
        NumberPanel panel = (NumberPanel) pane.getComponentsInLayer(0)[0];
        System.out.println("Panel #" + panel.getNumber());
        }
        for(int r = 7; r > 3; r--) {
            pane.remove(r);
        NumberPanel panel = (NumberPanel) pane.getComponentsInLayer(7)[0];
        System.out.println("Panel #" + panel.getNumber());
        }
        pack();
        setLocationRelativeTo(null);
    }
   
    private class NumberPanel extends JPanel {
       
        private final int n;
       
        public NumberPanel(int i, Dimension s) {
            super();
            setOpaque(false);
            setSize(s);
        n = i;   
        }
       
        public int getNumber() {
            return n;
        }
       
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
            g2.setColor(Color.BLACK);
            int cord = n + 1;
            g2.drawString(new Integer(n).toString(),
                    cord * 30,
                    cord * 30);
           
        g2.dispose();
        }
    }

    public static void main(String[] args) {
       
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new LayeredPain().setVisible(true);
            }
        });
    }
}

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Can anyone show me what I'm doing wrong?

P.S. I realize that if the layers I am trying to remove were actually removed then the application would not run because line 31 would cause an ArrayIndexOutOfBoundsException to be thrown if the layer at index 7 was actually removed when "pane.remove(7); "is called. I simply left it that way fror the purposes of demonstration and to allow anyone else to be able to compile and run the code.

Here's a snapshot of the example when run. As you can see from the source remove() is called with the ints 7, 6, 5 and 4 , but as you can see from the snapshot those layers are unchanged and instead layers 3, 2, 1. and 0 are removed. Can anyone show me what I am doing wrong?

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