Using BufferStrategy with Applet

[gamehacer2000]

I do not know whether anyone has posted a way to use BufferStrategy with an Applet or a JApplet. However,
I have recently created a class called AppletGameCore which acts as a facility to easily create games with Applet. I apologize for the lack of detailed comments.
Here is the

1   2   3   4   5   6   7   8   9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41   42   43   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   61   62   63   64   65   66   67   68   69   70   71   72   73   74   75   76   77   78   79   80   81   82   83   84   85   86   87   88   89   90   91   92   93   94   95   96   97   98   99   100   101   102   103   104   105   106   107

import java.awt.Canvas; import java.awt.Graphics2D; import java.awt.Dimension; import java.awt.image.BufferStrategy; import java.applet.Applet; /**  *AppletGameCore.java  *@author David Graham[font=Verdana][/font]  */   public abstract class AppletGameCore extends Applet implements Runnable {       private BufferStrategy bufferStrategy;       private Canvas drawArea;/*Drawing Canvas*/       private boolean stopped = false;/*True if the applet has been destroyed*/       private int x = 0;             public void init()       {             Thread t = new Thread(this);             drawArea = new Canvas();             setIgnoreRepaint(true);             t.start();       }             public void destroy()       {             stopped = true;                         /*Allow Applet to destroy any resources used by this applet*/             super.destroy();       }             public void update()       {             if(!bufferStrategy.contentsLost())             {                   //Show bufferStrategy                  bufferStrategy.show();             }       }             //Return drawArea's BufferStrategy      public BufferStrategy getBufferStrategy()       {             return bufferStrategy;       }             //Create drawArea's BufferStrategies      public void createBufferStrategy(int numBuffers)       {             drawArea.createBufferStrategy(numBuffers);       }             //Subclasses should override this method to do any drawing      public abstract void draw(Graphics2D g);             public void update(Graphics2D g)       {             g.setColor(g.getBackground());             g.fillRect(0,0,getWidth(),getHeight());       }             //Update any sprites, images, or primitives      public abstract void update(long time);             public Graphics2D getGraphics()       {             return (Graphics2D)bufferStrategy.getDrawGraphics();       }             //Do not override this method            public void run()       {             drawArea.setSize(new Dimension(getWidth(),getHeight()));             add(drawArea);             createBufferStrategy(2);             bufferStrategy = drawArea.getBufferStrategy();                         long startTime = System.currentTimeMillis();             long currTime = startTime;                         //animation loop            while(!stopped)             {                   //Get time past                  long elapsedTime = System.currentTimeMillis()-currTime;                   currTime += elapsedTime;                                     //Flip or show the back buffer                  update();                                     //Update any sprites or other graphical objects                  update(elapsedTime);                                     //Handle Drawing                  Graphics2D g = getGraphics();                   update(g);                   draw(g);                                     //Dispose of graphics context                  g.dispose();             }       } }

Feel free to modify and use this code for your own purposes.
If you have any questions or comments, please post them.  

Note: This code is only compatible with J2SE 1.4 and up.

True knowledge is admitting what you don't no.

Confucius I think...

[baylor]

David, first i wanted to say thanks. It sounds awful, but i spent 6 hours today looking for working code that shows an applet using BufferStrategy. i was begining to think it was impossible. So i was happy when i found this post

Now here's the problem - i don't exactly understand the code and i don't know how to use it. And it won't compile for me. Am i doing something wrong?

My biggest two questions:

1. How do things get drawn?
In normal applets, you call one of the repaint() methods which calls update() which clears the invalidated region then calls paint()
 repaint()->update()->paint()
But AppletGameCore doesn't have a repaint() or paint() method (you can not have a paint method?). And it has two update methods. It took me a while to realize that update(Graphics2D g) never gets called by the system. Because of the name i thought it was like update(), but it isn't, it just has the same name  

So my best guess here is that you've completely disabled Java's drawing/painting and have chosen to handle it entirely manually. Is that correct?

If so, out of curiosity, why is the paint routine named draw() rather than paint()? Would it have confused the system if it had been called paint()?

2. Does the code compile?
My compiler (Sun's J2SE 1.4.2) doesn't like the method
 public Graphics2D getGraphics()
That's because java.awt.Component already has a method called getGraphics() but it returns a Graphics rather than a Graphics2D. And since you can't have two methods that are identical except for return type...

i really, really want this code to work, but i've been screwing with it for a while and i can't figure out how to do it. Help?

-baylor

[swpalmer]

So my best guess here is that you've completely disabled Java's drawing/painting and have chosen to handle it entirely manually. Is that correct?

That is always the case when doing "active" painting with a BufferStrategy

If so, out of curiosity, why is the paint routine named draw() rather than paint()? Would it have confused the system if it had been called paint()?

You don't usually want the two painting strategies (sytem triggered update-paint vs. active rendering) to be fighting over the same space.   Specially when you have active drawing in a separate thread from the AWT event thread where "normal" painting occurs..

2. Does the code compile?
My compiler (Sun's J2SE 1.4.2) doesn't like the method
 public Graphics2D getGraphics()
That's because java.awt.Component already has a method called getGraphics() but it returns a Graphics rather than a Graphics2D. And since you can't have two methods that are identical except for return type...

I have not tried the code, but perhaps you can just change the return type to Graphics and be done with it?

Games published by our own members! Check 'em out!

[gamehacer2000]

First off, sorry for not replying. Been off for a while.
Thanks swpalmer for replying to baylor. For the most part your response was correct. Since you gave an good reply to baylor, I don't have to explain too much. The reason the getGraphics() method is problematic lies in the fact that you should not combine "active" and "passive" rendering. If you use paint and repaint, the methods request the getGraphics() of a component. To ensure that no calls request the standard getGraphics() method you should ignore repaint messages and stay away from overriding paint. Hope this is useful.