Look and Feel problem, help!

[cloudffx]

Here is my code:
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Test implements Runnable {

   public static void main(String args[]) {
      Test frame = new Test();
      new Thread(frame).start();
   }

   int width = 800;
   int height = 600;
   MyCanvas canvas;
   JFrame f = new JFrame();

   /**
    * Create the frame
    */
   public Test() {
      
      Skin.initSkin("res/skin/");

      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      f.setLayout(null);
      f.setSize(width, height);

      guiPanel = new JPanel();
      guiPanel.setLayout(null);
      guiPanel.setOpaque(false);
      guiPanel.setBounds(0, 0, width, height);
      f.add(guiPanel);
      addButton(guiPanel);

      canvas = new MyCanvas();
      canvas.setBounds(0, 30, width, height);
                                f.add(canvas);

      f.setVisible(true);
   }

   private void addButton(Container comp) {
      JButton b = new JButton("my button");
      b.setName("GameButton2");
      b.setBounds(100, 100, 100, 100);
      b.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            f.add(canvas);
         }
      });
      comp.add(b);

      b = new JButton("my button");
      b.setBounds(200, 100, 100, 100);
      comp.add(b);

      b = new JButton("my button");
      b.setBounds(200, 200, 100, 100);
      comp.add(b);

      b = new JButton("my button");
      b.setBounds(100, 200, 100, 100);
      comp.add(b);

      JTextField jtf = new JTextField();
      jtf.setBounds(0, 0, 300, 50);
      jtf.setName("PetTextfield");
      comp.add(jtf);

   }

   public void run() {
      while (true) {
         render();
         try {
            Thread.sleep(30);
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }
   }

   int frame = 0;
   private JPanel guiPanel;

   class MyCanvas extends Canvas {
      @Override
      public void paint(Graphics g) {
         frame += 5;
         if (frame > 255)
            frame = 0;
         g.setColor(new Color(frame));
         g.fillRect(0, 0, getWidth(), getHeight());
      }
   }

   public void render() {
      Graphics g = canvas.getGraphics();
      if (null == g)
         return;
      if (canvas.isVisible())
         canvas.paint(g);
   }

}

when I remove Skin.initSkin("res/skin/") , canvas render under all buttons, everything goes well, but when I add my custom look and feel skin, canvas render will cover all buttons. why? it's that look and feel problem? my jre version is "jre6 update 12"

[Mr_Light]

Do not mix heavyweight components with lightweight ones at the very least don't add heavyweight components to lightweight containers.

As for your actual question, I'm not sure if we have enough information.

[cloudffx]

Mr_Light, thank you!

I just want to use swing as my game gui, and I don't  want  to update swing components in my game loop, but let Swing update itself in the usual way. And when I add my custom skin, it doesn't work! anything wrong?