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Re: Drawing problem

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  To: comp.lang.java.gui
Robert Sturzenegger wrote:
>>> I would like to draw a graph in a container. Since the calculation of the 
>>> graph may be very time consuming, I would like to watch how the graph 
>>> builds up.

Michael Rauscher wrote:

>> If it's just for testing purposes, you could turn off Swing's double 
>> buffering. Otherwise Andrew Thompson's method is much preferred.

[Andrew Thompson suggested to remove the time consuming task from the EDT].

Robert Sturzenegger wrote:

> I tried this and it really accomplishes what I want. Since you stated, that 
> this solution should be for testing purposes only and that Andrew Thompson's 
> method would be the preferred one, I also wanted to try his way. However I 
> failed .... Details can be found in a response to his suggestion.

The key is to separate the 'current state' of the drawing from the 
drawing process.

E.g. you might want to use a BufferedImage as offscreen image. 
paintComponent simply draws that image on screen.

private BufferedImage img = new BufferedImage(400, 400,
         BufferedImage.TYPE_INT_ARGB);

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

In theory, you could now manipulate the image and call repaint to show 
the result on screen. In practice, this is possible, too. The only thing 
you'd have to care of, is to manipulate the image on the EDT.

So:

private void calculateAndPaint() {
     for ( int x = 0; x < 200; ++x ) {
         final int i = x;
         SwingUtilities.invokeLater( new Runnable() {
             public void run() {
                 Graphics g = img.createGraphics();
                 g.drawLine( i, i, i-1, i-1 );
                 g.dispose();
                 repaint();
             }
         });
         try { Thread.sleep(10); } catch ( InterruptedException e ) {}
     }
}

The last thing one has to do is to let calculateAndPaint be run on a new 
Thread:

public void paint() {
     Thread t = new Thread( new Runnable() {
         public void run() {
             calculateAndPaint();
         }
     });
     t.setPriority( Thread.NORM_PRIORITY );
     t.start();
}

Bye
Michael

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Drawing problem "Robert Sturzenegger" <robert.sturzenegger@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
  Re: Drawing problem "Andrew Thompson" <andrew.thompson@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
    Re: Drawing problem "Robert Sturzenegger" <robert.sturzenegger@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
  Re: Drawing problem "Michael Rauscher" <michael.rauscher@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
    Re: Drawing problem "Robert Sturzenegger" <robert.sturzenegger@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
      Re: Drawing problem "Michael Rauscher" <michael.rauscher@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
        Re: Drawing problem "Knute Johnson" <knute.johnson@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
          Re: Drawing problem "Michael Rauscher" <michael.rauscher@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
            Re: Drawing problem "Knute Johnson" <knute.johnson@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
              Re: Drawing problem "Michael Rauscher" <michael.rauscher@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
                Re: Drawing problem "Knute Johnson" <knute.johnson@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
                Re: Drawing problem "Michael Rauscher" <michael.rauscher@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000
        Re: Drawing problem "Robert Sturzenegger" <robert.sturzenegger@THRWHITE.remove-dii-this> - 2011-04-27 15:31 +0000

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