Java Panel Double Buffering

Question

Hey everyone, wondered if anyone could point me in the right directon, i have developed a pong game and it needs double buffering due to flickering. Iv tryed some of the post on here to try and make it work, but im still a beginner with the swing awt suff, any help would be amazing thanks.

public class PongPanel extends JPanel implements Runnable {

private int screenWidth = 500;
private int screenHeight = 300;

private boolean isPaused = false;
private boolean isGameOver = false;

private int playToPoints = 10;

private Padel player1,player2;
private Ball ball;

private Thread gameThread;
private Image dbImage;
private Graphics dbg; 

public PongPanel() {
   setPreferredSize(new Dimension(screenWidth,screenHeight));
   setBackground(Color.BLACK);
   setDoubleBuffered(true);
   setFocusable(true);
   requestFocus();

   player1 = new Padel(Position.LEFT,screenWidth,screenHeight);
   player2 = new Padel(Position.RIGHT,screenWidth,screenHeight);
   ball = new Ball(10,screenWidth/2,screenHeight/2,Color.WHITE);
}

public void addNotify(){
 super.addNotify();
   startGame();
}

private void startGame(){
  gameThread = new Thread(this);
  gameThread.start();
}

@Override
public void run() {
 while (!isGameOver) {   
 dbImage = createImage(screenWidth,screenHeight);
 dbg = this.getGraphics();
 if(!isPaused){
   if(!gameOverCheck()){
     updateGame();
     paintComponents(dbg);   
    }
 }else if(isPaused){
    dbg.setColor(Color.ORANGE);
    dbg.setFont(new Font("serif",Font.BOLD,50));
    dbg.drawString("Paused", screenWidth/2-82, screenHeight/2);
 } 
 try {
     Thread.sleep(30);
    } catch (InterruptedException e) {e.printStackTrace();}
   }
   }

  private boolean gameOverCheck(){
  if(player1.getScore() == playToPoints){
   dbg.setColor(player1.getColour());
   dbg.setFont(new Font("serif",Font.BOLD,50));
   dbg.drawString("Player 1 Wins!", screenWidth/2 - 161, screenHeight/2);
   setGameOver(true);
   return true;
  }else if(player2.getScore() == playToPoints){
   dbg.setColor(player2.getColour());   
   dbg.setFont(new Font("serif",Font.BOLD,50));
   dbg.drawString("Player 2 Wins!", screenWidth/2 - 161, screenHeight/2);
   setGameOver(true);
   return true;
  }

  return false;
 }

 private void updateGame(){
  ball.move(screenWidth,screenHeight,player1,player2);
  player1.aiForPadel(screenWidth, screenHeight, ball.getX(), ball.getY());
  player2.aiForPadel(screenWidth, screenHeight, ball.getX(), ball.getY());

 }

  @Override
  public void paintComponents(Graphics g) {
  super.paintComponents(g);
  dbg.setColor(Color.BLACK);
  dbg.fillRect(0, 0, screenWidth+20, screenHeight+20);
  dbg.setColor(Color.WHITE);
  dbg.drawLine(screenWidth/2, 0, screenWidth/2, screenHeight);
  dbg.setFont(new Font("serif",Font.BOLD,32));
  dbg.drawString(player1.getScore()+"", screenWidth/2-40, screenHeight - 20);
  dbg.drawString(player2.getScore()+"", screenWidth/2+20, screenHeight - 20);
  ball.drawBall(dbg);
    player1.drawPadel(dbg);
    player2.drawPadel(dbg);
 }
}

Answer 1

There's a really good tutorial here which describes how to use BufferStrategy to produce non-flickering animation.

The important points are:

• Call setIgnoreRepaint(true) on the top-level Canvas to prevent AWT from repainting it, as you'll typically be doing this yourself within the animation loop.
• Obtain the Graphics2D object from the BufferStrategy (rather than using the instance passed in via paintComponent(Graphics g).

Answer 2

A must-read about the painting mechanism in AWT and Swing

Painting in AWT and Swing