Pong Game - HELP

Question

Hi guys, I'd firstly like to apologise if I've posted in the wrong forum - as you've moved probably guessed, I'm new round "there here parts"! :P
I recently started attempting some basic java graphics in a swing. So far, everything is working but I have the following questions:
1) How do I stop the graphics flickering? - I know it's due to the thread refresh rate in the continuous loop, but can I stop the flickers?
2) How do I add a JPanel ABOVE the canvas in which I can add buttons to restart the game? - I assume it would involve a GridBagLayout which I'm unfamiliar with, so your assistance would be appreciated. Note: I'll only need assistance in adding the JPanel above the canvas, I can do the rest! :)
My current code is shown below - please don't complain about imperfections, as it's just a development:
import javax.swing.*;
import java.awt.image.*;
import java.awt.event.*;
import java.awt.*;
public class Pong
   private static JFrame frame;
   private static Canvas canvas;
   private static KeyListener listener;
   private static boolean inPlay = true;
   private static boolean gamePaused = false;
   private static int yP1 = 160;
   private static int yP2 = 160;
   private static Graphics Bgfx;
   private static boolean update = false;
   private static BufferedImage bi;
   private static int ballPosx = 600;
   private static int ballPosy = 200;
   private static int ballXSpeed = 1;
   private static int ballYSpeed = 1;
   private static int ballOffSetx = 1;
   private static int ballOffSety = -1;
   private static int paddleSpeed = 10;
   private static boolean winnerP1 = false;
   private static boolean winnerP2 = false;
   //Upper panel variables
   private static JPanel upperPNL;
   private static JButton restartButton;
   private static GridBagConstraints gbc;
   public static void main (String args[])
      //Initialize GUI
      frame = new JFrame("Pong Game");
       //Canvas / frame parameters
      canvas = new Canvas();
      canvas.setSize(1200, 500);
       //Content pane
       Container content = frame.getContentPane();
       content.add(canvas);
      frame.setIgnoreRepaint(true);                
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
      frame.pack();
      frame.setVisible(true);
       frame.addKeyListener(listener);
       frame.addKeyListener(new KeyListener() {
          public void keyPressed(KeyEvent e) {
               if (e.getKeyCode() == 'Q') {
                    if (yP1 > 20) {
                         yP1 -= paddleSpeed;
                         update = true;
                  if (e.getKeyCode() == 'A') {
                       if (yP1 < 380) {
                         yP1 += paddleSpeed;
                         update = true;
               if (e.getKeyCode() == 'P') {
                    if (yP2 > 20) {
                         yP2 -= paddleSpeed;
                         update = true;
               if (e.getKeyCode() == 'L') {
                    if (yP2 < 380) {
                         yP2 += paddleSpeed;
                         update = true;
               public void keyReleased(KeyEvent e) {
               update = false;
                public void keyTyped(KeyEvent e) {}
      gameLoop(canvas.getGraphics());                     //Begin Game Loop
   private static void gameLoop(final Graphics gfx)
      //Create a BufferedImage to use it's graphics.
      bi = new BufferedImage(1200, 500, BufferedImage.TYPE_INT_RGB);
      //While the game isn't paused
      while(inPlay)
     while(!gamePaused)
          try
                  Thread.sleep(1);
          catch(Exception ex)
               System.out.println("Interrupted Sleep");
          gameRender(bi, gfx);
          moveBall();
          checkCollisions();
   private static void moveBall()
          if (winnerP1 || winnerP2) { ballOffSety = 0; ballOffSetx = 0; }
          ballPosx += ballXSpeed * ballOffSetx;
          ballPosy += ballYSpeed * ballOffSety;
          if (ballPosy < 0) {
               ballOffSety *= -1;
          if (ballPosy > 500) {
               ballOffSety *= -1;
          if (ballPosx < 0) {
               ballOffSetx *= -1;
          if (ballPosx > 1200) {
               ballOffSetx *= -1;
     private static void checkCollisions() {
          if ((ballPosx >= 72 && ballPosx <= 107) && (ballPosy >= yP1 && ballPosy <= (yP1 + 100)))
               ballOffSetx *= -1;
          if ((ballPosx >= 1072 && ballPosx <= 1107) && (ballPosy >= yP2 && ballPosy <= (yP2 + 100)))
               ballOffSetx *= -1;
          if (ballPosx < 107)
               winnerP2 = true;
          if (ballPosx > 1107)
               winnerP1 = true;
   private static void gameRender(BufferedImage bi, Graphics gfx)
       if (winnerP1) {
          bi.getGraphics();
          Font font = new Font("Arial", Font.PLAIN, 36);
          gfx.setFont(font);
          gfx.setColor(Color.RED);
          gfx.drawString("PLAYER 1 WINS!!!", 520, 200);
          gfx.drawImage(bi, 0, 0, null);
       if (winnerP2) {
          bi.getGraphics();
          Font font = new Font("Arial", Font.PLAIN, 36);
          gfx.setFont(font);
          gfx.setColor(Color.RED);
          gfx.drawString("PLAYER 2 WINS!!", 520, 200);
          gfx.drawImage(bi, 0, 0, null);
      //Get Buffered Graphics to Draw To
      Bgfx = bi.getGraphics();
      //Draw Background
      Bgfx.setColor(Color.BLACK);
      Bgfx.fillRect(0,0,1200,500);
      //Draw Bar 1
      gfx.setColor(Color.GREEN);
       gfx.fillRect(72,yP1,35,100);
      //Draw Bar 2
      gfx.fillRect(1072,yP2,35,100);
      //Draw Ball
      gfx.fillRect(ballPosx,ballPosy,20,20);
      //Draw the Buffered Graphics to the screen
      gfx.drawImage(bi, 0, 0, null);
}Constructive criticism is welcomed, but major edits which I'm not likely to understand as of yet are not.
Many thanks for your assistance, it's appreciated.
Edited by: -Barto- on Jun 30, 2010 5:21 PM

Answer 1

-Barto- wrote:
Hi guys, I'd firstly like to apologise if I've posted in the wrong forum - as you've moved probably guessed, I'm new round "there here parts"! :PWelcome, and not to worry -- this is the correct forum for your question.
I recently started attempting some basic java graphics in a swing. So far, everything is working but I have the following questions:
1) How do I stop the graphics flickering? - I know it's due to the thread refresh rate in the continuous loop, but can I stop the flickers?
2) How do I add a JPanel ABOVE the canvas in which I can add buttons to restart the game? - I assume it would involve a GridBagLayout which I'm unfamiliar with, so I think that you're main problem is that you're trying to mix AWT components (i.e., Canvas) and Swing components (everything else) in one program. In addition, you need to update your game loop and graphics to be in line with Swing best practices. So, get rid of Canvas, read up in the tutorials on how to do graphics in Swing (using paintComponent override for instance) and use a Swing Timer for your Game loop and you'll be half way there. Best of luck!