Double buffer problems

[freeridin101]

im having problems with my double buffer. i have have read through many other posts and have come up with nothing. im getting pretty desprite so any pointer as to why this wont work or a more efficient way of doing this would be great.

code:

import java.applet.*; import java.awt.event.*; import java.awt.*; public class DoubleBuffering extends Applet {     int y, score, direction;     Graphics bufferGraphics;     Image offscreen;     Dimension dim;     static void delay (int del)     {         try         {             Thread.sleep (del * 1000);         }         catch (InterruptedException e)         {         }     }     public static void delay (int del)     {         for (int d = 1 ; d < del ; d++)         {             for (int x = 1 ; x < 30000 ; x++)             {            }         }     }     public void eraseship (int x, int y)     {         Graphics g = getGraphics ();         g.setColor (Color.white);         g.fillOval (x, y, 10, 20);         g.fillOval (x - 10, y + 10, 30, 10);         g.fillOval (x + 3, y + 4, 4, 4);     }     public void init ()     {         dim = getSize ();         offscreen = createImage (dim.width, dim.height);         direction = 1;         y = 10;         score = 0;         resize (800, 600);         while (score < 10)         {             y = y + direction;             drawship (10, y);             delay (2);             eraseship (10, y);             if (y > 590)                 direction = -1;             if (y < 0)                 direction = 1;         }         bufferGraphics = offscreen.getGraphics ();     }     public void paint (Graphics g)     {         bufferGraphics.clearRect (0, 0, dim.width, dim.width);         g.drawImage (offscreen, 0, 0, this);     }     public void update (Graphics g)     {         paint (g);     }     public void drawship (int x, int y)     {         Graphics g = getGraphics ();         g.setColor (Color.green);         g.fillOval (x, y, 10, 20);         g.setColor (Color.red);         g.fillOval (x - 10, y + 10, 30, 10);         g.setColor (Color.black);         g.fillOval (x + 3, y + 4, 4, 4);     } }

[freeridin101]

sorry frogot to delete this part


public static void delay (int del)
{
for (int d = 1 ; d < del ; d++)
{
for (int x = 1 ; x < 30000 ; x++)
{
}
}
}

[freeridin101]

anyone abile tofigure this out. i need help please. just give me a point to start fixing at. it is most likly all wrong so anything at this point would be great

[freeridin101]

Come on guys. i no someone on here knows how to do this.im still trying and its still not working. help me. post something. atleast tell me if its all wrong. so i can start again. tell me something

[freeridin101]

Moderator help maybe

[[Gandalf]]

Please avoid quintuple-posting, or else you will not get a positive response from users here. The chances of you getting a helpful response will go below 0%.

Use the search button next time, this has been brought up multiple times.

Here you will find a useful example:
http://compsci.ca/v2/viewtopic.php?t=3740

[freeridin101]

I have already ready through that post(4times)and cannot figure out how to apply that to my program which is why i then quintuple-posted trying to get help. if u can explain how to apply this to my program (not do it for me) that would be great.

[McKenzie]

So many errors. The two biggest ones; You are not using your double buffer correctly. You are trying to treat it like it's Turing and are trying to erase by drawing in white when in fact you should be repainting the entire scene on the offscreen buffer then copying onscreen. Second: Your main game loop does not work because the applet is not fully constructed and you are trying to draw on it. Take a look here:
http://javaboutique.internet.com/tutorials/Java_Game_Programming/
It's a great site for the basics. To find a great site for advanced stuff Google "Killer Game Java" and check the first hit.

[freeridin101]

okay i think im getting closer but i now need help getting this to run

code:

import java.applet.*; import java.awt.event.*; import java.awt.*; import java.lang.Object.*; import java.awt.Image.*; public class DoubleBuffering extends Applet {     int y, score, direction;     Graphics bufferg;     BufferedImage buffer;     static void delay (int del)     {         try         {             Thread.sleep (del * 1000);         }         catch (InterruptedException e)         {         }     }     public void eraseship (int x, int y)     {         Graphics g = getGraphics ();         g.setColor (Color.white);         g.fillOval (x, y, 10, 20);         g.fillOval (x - 10, y + 10, 30, 10);         g.fillOval (x + 3, y + 4, 4, 4);     }     public void init ()     {         direction = 1;         y = 10;         score = 0;         resize (800, 600);         while (score < 10)         {             y = y + direction;             drawship (10, y);             delay (30);             eraseship (10, y);             if (y > 590)                 direction = -1;             if (y < 0)                 direction = 1;         }         gameLoop ();     }     public void drawship (int x, int y)     {         bufferg.setColor (Color.green);         bufferg.fillOval (x, y, 10, 20);         bufferg.setColor (Color.red);         bufferg.fillOval (x - 10, y + 10, 30, 10);         bufferg.setColor (Color.black);         bufferg.fillOval (x + 3, y + 4, 4, 4);     }     public void gameLoop ()     {        // drawship (1,y);         drawBufferToScreen ();     }     public void drawBufferToScreen ()     {         Graphics g = getGraphics ();         g.drawImage (buffer, 0, 0, null);     }     public void paint (Graphics g)     {     } }

[rizzix]

here's a BIG hint: do NOT put your game-loop in the init method.

[McKenzie]

Still has many errors. Lets look at the one that Rizzix is talking about. Your main game loop (the while you have in init, not the method you call gameLoop) can not be in init because the Applet is not fully constructed. Try

code:

System.out.println(this.getHeight());

anywhere you are thinking of drawing to your applet and if you get 0 you know it's not there yet.
It looks like you are trying to avoid using threads here because you don't understand them. It is wise to avoid using things you don't understand. You have two choices. Learn threads (well, enough to use them here) or have the user click some button or press a key to start the action.

[freeridin101]

i must be getting closer here is another attempt at this after the help you guys have given me (thanks by the way):

code:

import java.applet.*; import java.awt.*; public class doublebufferball extends Applet implements Runnable {     int y, score, direction;     private Image dbImage;     private Graphics dbg;     static Graphics g;     static void delay (int del)     {         try         {             Thread.sleep (del * 10);         }         catch (InterruptedException e)         {         }     }     public void init ()     {         {             direction = 1;             y = 10;             score = 0;             resize (800, 600);             while (score < 10)             {                 y = y + direction;                 drawship (10, y);                 delay (1);                 eraseship (10, y);                 if (y > 590)                     direction = -1;                 if (y < 0)                     direction = 1;             }         }     }     public void start ()     {         Thread th = new Thread (this);         th.start ();     }     public void stop ()     {     }     public void destroy ()     {     }     public void run ()     {         Thread.currentThread ().setPriority (Thread.MIN_PRIORITY);         while (true)         {             repaint ();             // try             // {             //     Thread.sleep (30);             // }             // catch (InterruptedException ex)             // {             //             // }             Thread.currentThread ().setPriority (Thread.MAX_PRIORITY);         }     }     public void update (Graphics g)     {         if (dbImage == null)         {             dbImage = createImage (this.getSize ().width, this.getSize ().height);             dbg = dbImage.getGraphics ();         }         dbg.setColor (getBackground ());         dbg.fillRect (0, 0, this.getSize ().width, this.getSize ().height);         dbg.setColor (getForeground ());         paint (dbg);         g.drawImage (dbImage, 0, 0, this);     }     public void drawship (int x, int y)     {         g = getGraphics ();         g.setColor (Color.green);         g.fillOval (x, y, 10, 20);         g.setColor (Color.red);         g.fillOval (x - 10, y + 10, 30, 10);         g.setColor (Color.black);         g.fillOval (x + 3, y + 4, 4, 4);     }     public void eraseship (int x, int y)     {         Graphics g = getGraphics ();         g.setColor (Color.white);         g.fillOval (x, y, 10, 20);         g.fillOval (x - 10, y + 10, 30, 10);         g.fillOval (x + 3, y + 4, 4, 4);     }     public void paint (Graphics g)     {     } }

That runs for me but there is still some flickering what part is wrong?

[rizzix]

i'm supprised it worked... you haven't changed what we asked you to change.. =/

move your game-loop aka the "big while loop" out of the init method into, well maybe the paint method.

Oh and please aviod threads, for now. (although this pertty much means you should not use any gui components in your game either. for now anyway)

[freeridin101]

rizzix i tryed to move the main game loop into the paint method but when i do my program runs but freezes and goes crazy try it you'll see what i mean

i just learned threads because McKenzie said i had to learn them to do this. im so confused

[rizzix]

McKenzie's intentions are honourable but I believe its too early Threads slove a lot of annoying issues.. but they add a whole new level of complexity.

anyway let me try and fix your code my self.. =/