Java JFrame paint method display flickers

Question

while using paint from JFrame, my display flickers a lot. I can't make it stop and I would love to know how to make it stop flickering. I also tried to add the swing.timer here, but its still doesn't do anything. package Game;

public class Play extends JFrame implements MouseMotionListener, MouseListener, KeyListener, ActionListener {
    
    private int _xPad,_yPad,_xdir,_ydir;
    private Brick[][] _bricks;
    private Ball _gameBall;
    private Timer _timer;
    
    public Play(int[][] board){
        super("Elemental Brick Breaker");
        _xdir = 0;
        _ydir = 0;
        _xPad = 350;
        _yPad = 500;
        _timer = new Timer(1000,this);
        _timer.start();
        _gameBall = new FireBall(_xPad,_yPad);
        _bricks = new Brick[8][10];
        int x = 75, y = 40;
        for(int i = 0 ; i < 8 ; i++) {
            for(int j = 0 ; j < 10 ; j++) {
                _bricks[i][j] = new FireBrick(x,y);
                x = x + 65;
                }
            y = y + 25;
            x = 75;
        }
    }

    public void paint(Graphics g) {
        super.paint(g);
        g.fillRect(_xPad, _yPad, 120, 10);
        for(int i = 0 ; i < 8 ; i++) {
            for(int j = 0 ; j < 10 ; j++) {
                g.fillRect(_bricks[i][j].getX(), _bricks[i][j].getY() , 60, 20);
                }
        }
    }

    @Override
    public void actionPerformed(ActionEvent arg0) {
        // TODO Auto-generated method stub
        
    }
}

Answer 1

You can try this approach:

have a separate image to draw things on:

im=createImage(getWidth(), getHeight());

in constructor.

Then in paint:

Graphics g2=im.getGraphics();

and apply all commands relagated to g on g2:

g2.fillRect etc

then draw the image on g:

g.drawImage(im, 0, 0, this);

in short:

public void paint(Graphics g) {
    Graphics g2=im.getGraphics();
    g2.fillRect(_xPad, _yPad, 120, 10);
    for(int i = 0 ; i < 8 ; i++) {
        for(int j = 0 ; j < 10 ; j++) {
            g2.fillRect(_bricks[i][j].getX(), _bricks[i][j].getY() , 60, 20);
            }

    g.drawImage(im, 0, 0, this);
    }
}

and have an update method:

public void update(Graphics g) { paint(g); }

--

I have simplified your class as follows: - it does not produce flicker - if I put it back as you have it it produces flicker.

class Play extends JFrame implements ActionListener {

private int _xPad,_yPad,_xdir,_ydir;
private Rectangle[][] _bricks;
//    private Ball _gameBall;
private javax.swing.Timer _timer;
Image im;

public Play(){
    super("Elemental Brick Breaker");
    setSize(1000, 500);
    _xdir = 0;
    _ydir = 0;
    _xPad = 350;
    _yPad = 500;
    _timer = new javax.swing.Timer(1000,this);
    _timer.start();
//        _gameBall = new FireBall(_xPad,_yPad);
    _bricks = new Rectangle[8][10];
    int x = 75, y = 40;
    for(int i = 0 ; i < 8 ; i++) {
        for(int j = 0 ; j < 10 ; j++) {
            _bricks[i][j] = new Rectangle(x,y, 60, 20);
            x = x + 65;
            }
        y = y + 25;
        x = 75;
    }
    setVisible(true);
    im=createImage(getWidth(), getHeight());
}

public void paint(Graphics g) {
    Graphics g2=im.getGraphics();
    g2.fillRect(_xPad, _yPad, 120, 10);
    for(int i = 0 ; i < 8 ; i++) {
        for(int j = 0 ; j < 10 ; j++) {
            g2.fillRect(_bricks[i][j].x, _bricks[i][j].y , 60, 20);
            }
    }
    g.drawImage(im, 0, 0, this);
}

public void update(Graphics g) { paint(g); }

@Override
public void actionPerformed(ActionEvent arg0) {
    // TODO Auto-generated method stub
  repaint();
  System.out.println("t");
}
}