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Article #17853

Simple ??? double buffering

#17853
From: Rich Downing
Date: Fri, 11 Sep 1998 00:00
70 lines
2347 bytes
Alright folks,

I'm obviously missing something simple here.  In the rather trivial
example that follows, the image is never shown on the screen. If I
comment out the offScreenGraphics.drawImage statement and uncomment
the offScreenGraphics.drawString statement the string will show
correctly.

I know that the url and images names are ok, because the image
displays correctly if I don't double buffer.

Any idea what is going on????

Thanks,

Rich

-------------------- code follows
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.net.*;

public class Omega extends Applet
{
  String cam1 = "myimage.jpg";
  Image cam1Image, offScreenImage;
  Graphics offScreenGraphics;

  public Omega()
    {  }

  public void init()
    {  this.setSize(400,300);  }
    
  public void start()
    { repaint();  }

  public void stop()
    { }

  public void destroy()
    { offScreenGraphics.dispose();  }

  public void paint(Graphics g)
    {
    if (cam1Image == null)
       {
       URL myurl = getDocumentBase();
       offScreenImage = createImage(400, 300);
       offScreenGraphics = offScreenImage.getGraphics();

       cam1Image = getImage(myurl, cam1);
       offScreenGraphics.drawImage(cam1Image, 0, 0, 400, 300, this);
//    offScreenGraphics.drawString("A Test",30,30);
       }

    g.drawImage(offScreenImage, 0, 0, 400, 300, this);
    }

  public void update(Graphics g)
    { paint(g); }
}

----------------------------------------------------------------------
Richard V. Downing                Home: http://rvd.home.mindspring.com
Senior Software Engineer                     Work: http://www.vsin.com   
VideoConferencing Systems, Inc.              Email: rvd@mindspring.com
Norcross, Ga
------------ When surrounded by wolves 'tis best to howl -------------
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From: rvd@mindspring.com (Rich Downing)
Subject: Simple ??? double buffering
Date: 1998/09/11
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