Re: a tight game loop in Swing

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.gui

Date:

Tue, 05 Jun 2012 21:51:11 -0700

Message-ID:

<jqmnk0$2jm$1@dont-email.me>

On 6/4/2012 4:39 PM, Lew wrote:

John B. Matthews wrote:

This reminds of an example adduced by Knute Johnson:

<https://groups.google.com/d/msg/comp.lang.java.gui/aBy_DZFvg2M/-T9aWOwBM-QJ>

Ten points for using the word "adduced".

There are some EDT violations in the cited code's 'main()' routine.

Here's the updated code with that fixed.

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.*;
import java.lang.reflect.*;
import javax.swing.*;

public class test3 extends JPanel implements Runnable {
     volatile BufferedImage bi;
     volatile long then;
     long now,time;
     final Thread thread;
     double angle,rate;
     int n;

     public test3() {
         super(false);
         setPreferredSize(new Dimension(400,300));

         thread = new Thread(this);

         addComponentListener(new ComponentAdapter() {
             public void componentResized(ComponentEvent ce) {
                 GraphicsConfiguration gc = getGraphicsConfiguration();
                 bi = gc.createCompatibleImage(getWidth(),getHeight());
             }
         });
     }

     public void start() {
         then = System.nanoTime();
         thread.start();
     }

     public void stop() {
         thread.interrupt();
     }

     public void run() {
         try {
             long now = 0;
             long then = System.nanoTime();

             while (true) {
                 render();
                 try {
                     EventQueue.invokeAndWait(new Runnable() {
                         public void run() {
                             paintImmediately(getBounds());
                         }
                     });
                 } catch (InvocationTargetException ite) {
                     System.out.println(ite);
                 }

                 /*
                 while (now < then + 10000000)
                     now = System.nanoTime();
                 then = now;
                 */
             }
         } catch (InterruptedException ie) {
             System.out.println(ie);
         }
     }

     public void render() {
         int w = getWidth();
         int h = getHeight();

         Graphics2D g = bi.createGraphics();
         g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
          RenderingHints.VALUE_ANTIALIAS_ON);

         g.setColor(Color.WHITE);
         g.fillRect(0,0,w,h);

         if (++n % 100 == 0) {
             now = System.nanoTime();
             time = now - then;
             then = now;
             rate = 100000000000.0 / time;
         }
         g.setColor(Color.RED);
         g.drawString(String.format("%5.1f",rate),10,12);

         angle += 0.001;
         g.rotate(angle,w/2,h/2);
         g.setColor(Color.BLUE);
         g.fillRect(w/2 - 100,h/2 - 100,200,200);

         g.dispose();
     }

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

     public static void main(String[] args) {
         EventQueue.invokeLater(new Runnable() {
             public void run() {
                 final test3 t3 = new test3();
                 final JFrame f = new JFrame();
                 f.addWindowListener(new WindowAdapter() {
                     public void windowOpened(WindowEvent we) {
                         t3.start();
                     }
                     public void windowClosing(WindowEvent we) {
                         t3.stop();
                         f.dispose();
                     }
                 });
                 f.add(t3,BorderLayout.CENTER);
                 f.pack();
                 f.setVisible(true);
             }
         });

     }
}