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From: "Andrew Thompson" <andrew.thompson@THRWHITE.remove-dii-this>
Subject: Re: Graphics and JVMs
Message-ID: <7abdeb2ca253a@uwe>
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Date: Wed, 27 Apr 2011 15:40:46 GMT
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.gui:2718

  To: comp.lang.java.gui
sshark@gmail.com wrote:
..
>...Is this has
>to do with the way I have written the code ..(?)

Yes.  At least, most of it is, since the code made a variety
of mistakes, such as using the 'push' model for Graphics.
Very unreliable and unpredictable behaviour (as you noticed).

Instead, the JFrame should be painted the same way you have 
the panel, by overriding the paint()/paintComponent() method.

There is still some flickering in this example*.  to remove that,
you might use an Image (more probably BufferedImage) as a 
backing store to write all the Graphics to, then simply 
Graphics.drawImage() it, once done.

Also, please watch the line length when posting to usenet.
It is best to keep line width under around 62 chars.  I fixed**
that for this example by moving the thread comment to the
previous line.

**Here is a tool that helps check text width.
<http://www.physci.org/twc.jnlp>

* E.G.
<sscce>
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;

   public class TestRandomBoxes extends JFrame {
       private Random pointRandomizer = new Random();
       String message = "Hi There";

       public TestRandomBoxes() {

           final JPanel p = new JPanel() {
               @Override
               // override paintComponent() for Swing *
               public void paintComponent(Graphics g) {
                   g.setColor(getBackground());
                   g.fillRect(0, 0, 200, 200);
                   g.setColor(Color.BLACK);
                   g.fillRect(50 + randomPoint().x,
                     50 + randomPoint().y, 50, 50);
               }
           };
           p.setPreferredSize(new Dimension(200, 200));

           Thread animator = new Thread() {
               @Override
               public void run() {
                   while (true) {
                       // repaint the entire frame
                       repaint();
                       try {
                           // reduce to increase update speed
                           Thread.sleep(200);
                       } catch (InterruptedException e) {
                           e.printStackTrace();
                       }
                   }
               }
           };
           animator.start();

           getContentPane().add(new JScrollPane(p));
       }

       // Except for Swing root components, use 'paint()'.
       // but then, it is unwise to be rendering directly
       // to root components.  Better to render to a
       // JPanel and add it to the root component.
       public void paint(Graphics g) {
           super.paint(g);

           if (message.length() < 1) {
               return;
           }

           int x=50;
           int y=50;

           int w = g.getFontMetrics().stringWidth(message)
             + 10;
           int h = g.getFontMetrics().getHeight() + 4;

           g.setColor(new Color(0x33, 0xFF, 0xFF, 50));
           g.fillRect(x, y, w, h);
           g.setColor(new Color(0x33, 0xFF, 0xFF));
           g.drawRect(x, y, w, h);
           g.setColor(Color.BLACK);
           g.drawString(message, x, (y + h - 4));
       }

       private Point randomPoint() {
           return new Point(pointRandomizer.nextInt(50),
               pointRandomizer.nextInt(50));
       }

       public static void main(String[] args) {
           TestRandomBoxes sl = new TestRandomBoxes();
           sl.pack();
           sl.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
           sl.setBounds(100, 100, 300, 300);

           // move the setVisible to last..
           sl.setVisible(true);
       }
}
</sscce>

-- 
Andrew Thompson
http://www.athompson.info/andrew/

Message posted via JavaKB.com
http://www.javakb.com/Uwe/Forums.aspx/java-gui/200711/1

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