problem with paint methods

[anomyth kumar]

this is the code which draws the star image to the frame

package skeleton;

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Board extends JPanel implements ActionListener{
Image star;
int x;
int y;
Timer timer=null;
 public Board() {
    star=new ImageIcon("img/star.png").getImage();
     x=0;y=0;
    
     timer =new Timer(25,this);
     timer.start();
	}
	 
@Override
protected void paintComponent(Graphics arg0) {
    Graphics2D graphics2D=(Graphics2D)arg0;
    graphics2D.drawImage(star, x, y, null);
}

 		public void actionPerformed(ActionEvent arg0) {
 			x++;y++;
 			if(y==540)
 			{
 				x=0;
 				y=0;
 			}
  repaint();
 		}		
}


package skeleton;

import javax.swing.JFrame;

public class Image1 extends JFrame{

	public Image1() {
		add(new Board());
		setResizable(true);
		setVisible(true);
 		setSize(800,600);
		setTitle(" example");
	}
	
	
	public static void main(String[] args) {
		try {
			Image1 image = new Image1();
		} catch (Exception e) {
		e.printStackTrace();
		}	
	}
}
   

while using the normal paint method it refreshes the frame and draws the star image but while using the paintcomponent method the image is getting dragged and while using paintchildren the image is drawn as that of normal paint method

would anybody explain what is exactly happening and the difference between these three paint methods.

[Ulf Dittmer]

Start here: http://java.sun.com/docs/books/tutorial/uiswing/painting/index.html

[Chris Nash]

I don't see where y is getting set to anything but 0, but I didn't do an exhaustive examination of the code. I think your problem is here:

@Override
protected void paintComponent(Graphics arg0) {
    Graphics2D graphics2D=(Graphics2D)arg0;
    graphics2D.drawImage(star, x, y, null);
}

Try this instead:

@Override
protected void paintComponent(Graphics arg0) {
    super.paintComponent(arg0);
    Graphics2D graphics2D=(Graphics2D)arg0;  // don't need to cast this to a Graphics2D--not an error, just don't need it for drawing an Image
    graphics2D.drawImage(star, x, y, null);
}

Calling the super method makes it behave like a regular JComponent, but still implements your painting. You may have to set the component to transparent (setOpaque(false)), but other than that, it should behave like you expect it to. HTH