Extending JPanel changes JPanel behavior

Question

All,
I am trying to center a JPanel in the middle of my JFrame. Below is the code I use to center the JPanel. What is confusing me is that when the panel in question, actionPnl, is declared as a JPanel, the centering code works beautifully. When I declare it as a CanvasPanel (see code below) it does not show up at all. Now, I thought that when you use �Extends� that the class you are creating inherits all attributes of the class you are extending however this behavior suggests otherwise. Am I overlooking some fundamental ingredient?
//private CanvasPanel actionPnl = new CanvasPanel();
private JPanel actionPnl = new JPanel();
private Box xp = Box.createHorizontalBox();
private Box yp = Box.createVerticalBox();
private void center()
  xp.add(Box.createHorizontalGlue());
  xp.add(actionPnl);
  xp.add(Box.createHorizontalGlue());
  yp.add(Box.createVerticalGlue());
  yp.add(xp);
  yp.add(Box.createVerticalGlue());
}//end center()
public class CanvasPanel extends JPanel
  private Image image;
public CanvasPanel()
   setBackground (Color.WHITE);
   setPreferredSize(new Dimension(600, 100));
}//end constructor CanvasPanel()
public void paintComponent(Graphics g)
   g.drawImage(image, 0, 0, null);
   g.dispose();
public void setImage(Image inImage)
   image = inImage;
}

Answer 1

We never want to see you entire program. We only want
to see the code that demonstrates the incorrect
behaviourI pieced this together and it has the same behavior. It is what I would call "hack code" and does not follow good practices. But it gets the point across. Just toggle which actionPnl declaration to comment out to see the difference.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.JPanel;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.image.BufferedImage;
import java.awt.Graphics;
public class test extends JFrame
Container c;
boolean btnControl = false;
/******** toggle these two *********/
//private CanvasPanel actionPnl = new CanvasPanel();
private JPanel actionPnl = new JPanel();
private Box xp = Box.createHorizontalBox();
private Box yp = Box.createVerticalBox();
public test()
//container
c = getContentPane();
c.setBackground(Color.BLACK);
c.setLayout(new BorderLayout());
//construction
buildActionPnl();
//add to JFrame
c.add(yp, BorderLayout.CENTER);
setSize(1200, 950);
setVisible(true);     
}//end constructor balance()
private void buildActionPnl()
  center();
}//end buildActionPnl()
private void center()
  xp.add(Box.createHorizontalGlue());
  xp.add(actionPnl);
  xp.add(Box.createHorizontalGlue());
  yp.add(Box.createVerticalGlue());
  yp.add(xp);
  yp.add(Box.createVerticalGlue());
}//end center()
public static void main(String args[])
  test t = new test();
t.addWindowListener(
            new WindowAdapter(){
                 public void windowClosing(WindowEvent we){
                      System.exit(0);
public class CanvasPanel extends JPanel
  private Image image;
public CanvasPanel()
   setBackground (Color.WHITE);
   setPreferredSize(new Dimension(600, 100));
}//end constructor CanvasPanel()
public void paintComponent(Graphics g)
   g.drawImage(image, 0, 0, null);
   g.dispose();
}I will research your suggested LayoutManager information and get back with how it works for me. At the moment I do not have code to control where each image is painted, that is what I am trying to take on.
Thanks for the help, it is appreciated!