Problem with basic JFrame layout manager

Mark Space <>
Thu, 04 Oct 2007 23:18:17 GMT
Hey all, here's a problem I can't lick.

Using just a basic JFrame, it should have a basic BorderLayout layout
manager by default. The docs strongly imply it, and it's manifest in
the code (source and runtime).

However, if I add my own component to the content pane, the JFrame when
displayed is as small as possible, only just large enough to display
it's decorations. I implement all the size methods, and it still
doesn't seem to do anything with them.

Does anyone know what I might be doing wrong?

Sample code follows. If I print out the classes involved (the first and
the second commented-out blocks) everything is as you'd expect. A
BorderLayout is present by default.

If I manually set the size of the content pane (first and third
commented-out blocks), the display is correct.

  * Created on Oct 3, 2007, 12:38:11 PM

package captcha.oak;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.LayoutManager;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import static javax.swing.WindowConstants.*;

public class Captcha extends java.awt.Component {

     private static final int WIDTH = 250;
     private static final int HEIGHT = 85;
     private BufferedImage image;

     /** Creates and displays a test captcha.
      * @param args The command line arguments are ignored.
     public static void main(String[] args) {
         // TODO code application logic here
         Captcha c = new Captcha();
         JFrame jf = new JFrame("Captcha");

         jf.getContentPane().add(c, BorderLayout.CENTER);

// java.awt.Container cp = jf.getContentPane();

// LayoutManager lm = cp.getLayout();
// System.err.println( cp.getClass().getName()+":: "+cp);
// System.err.println( lm.getClass().getName()+"::"+lm );
// System.err.println( lm.getClass().getSuperclass().getName());

// cp.setPreferredSize(c.getPerferredSize());



     public Captcha() {

         int[] data = new int[WIDTH * HEIGHT];

         for (int i = 0; i < data.length; i++) {
             int red = randomInt(255);
             int green = randomInt(255);
             int blue = randomInt(255);
             data[i] = (red << 16) | (green << 8) | blue;
         this.image = new BufferedImage(WIDTH, HEIGHT,
         image.setRGB(0, 0, WIDTH, HEIGHT, data, 0, WIDTH);

     private int randomInt(int i) {
         return (int) (java.lang.Math.random()* i);

     public void paint(Graphics g) {
         g.drawImage(image, 0, 0, this);

     public Dimension getPerferredSize()
         return getSize();
     public Dimension getSize()
         return new Dimension(WIDTH,HEIGHT);

     public Dimension getMaximumSize()
         return getSize();

     public Dimension getMinimumSize()
         return getSize();

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