Re: Graphics - how to show partial progress.

Knute Johnson <>
Wed, 02 Jan 2008 18:02:44 -0800
rossum wrote:

On Wed, 02 Jan 2008 10:23:08 -0800, Knute Johnson
<> wrote:

I'm not sure why this has to be so complicated. One image should be

I have two threads, one is creating the image in the background and
the other is displaying it in the Event Dispatch Thread. I want to
avoid any possibility of clashes between these two threads, hence I
need two copies of the image - one for each thread.

What can clash? The job of repaint() is to schedule a paint on the EDT.
  repaint() can be called from any thread.

Also, I don't think I would change the size of my component in
the paintComponent().

No, normally I would put it in an onResize Event, but I just stuck it
there for my test program in order to simplify things.

Why can't you just call repaint() periodically in your drawing code?

I do, indirectly through the publish/process mechanism.


You are moving a lot more data around and keeping two copies of the same
image. Doesn't seem too efficient to me. See below for a simplified

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;

public class test2 extends JPanel implements Runnable {
     final BufferedImage image;
     final Graphics g;

     public test2() {
         image = new BufferedImage(400,300,BufferedImage.TYPE_INT_ARGB);
         g = image.createGraphics();
         setPreferredSize(new Dimension(400,300));

     public void run() {
         for (int x=0; x<400; x++) {
             for (int y=0; y<300; y++) {
                 try { Thread.sleep(1);
                 } catch (InterruptedException ie) { }

     public void draw() {
         new Thread(this).start();

     public void paintComponent(Graphics g) {

     public static void main(String[] args) {
         EventQueue.invokeLater(new Runnable() {
             public void run() {
                 JFrame f = new JFrame();
                 final test2 t2 = new test2();
                 JButton b = new JButton("Draw");
                 b.addActionListener(new ActionListener() {
                     public void actionPerformed(ActionEvent ae) {


Knute Johnson
email s/nospam/knute/

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