Re: Graphics - how to show partial progress.

From:
Knute Johnson <nospam@rabbitbrush.frazmtn.com>
Newsgroups:
comp.lang.java.help
Date:
Wed, 02 Jan 2008 18:02:44 -0800
Message-ID:
<477c4244$0$1558$b9f67a60@news.newsdemon.com>
rossum wrote:

On Wed, 02 Jan 2008 10:23:08 -0800, Knute Johnson
<nospam@rabbitbrush.frazmtn.com> wrote:

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

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.

rossum


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
example.

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() {
         g.setColor(Color.WHITE);
         g.fillRect(0,0,image.getWidth(),image.getHeight());
         g.setColor(Color.BLUE);
         for (int x=0; x<400; x++) {
             for (int y=0; y<300; y++) {
                 g.drawLine(x,y,x,y);
                 try { Thread.sleep(1);
                 } catch (InterruptedException ie) { }
             }
             repaint();
         }
     }

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

     public void paintComponent(Graphics g) {
         g.drawImage(image,0,0,null);
     }

     public static void main(String[] args) {
         EventQueue.invokeLater(new Runnable() {
             public void run() {
                 JFrame f = new JFrame();
                 f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                 final test2 t2 = new test2();
                 f.add(t2,BorderLayout.CENTER);
                 JButton b = new JButton("Draw");
                 b.addActionListener(new ActionListener() {
                     public void actionPerformed(ActionEvent ae) {
                         t2.draw();
                     }
                 });
                 f.add(b,BorderLayout.SOUTH);
                 f.pack();
                 f.setVisible(true);
             }
         });
     }
}

--

Knute Johnson
email s/nospam/knute/

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