Flickering issues with a pong game

Question

Hello I am having these flickering issues with this pong game, and was hoping someone else could steer me in the right direction. been at this for like an hour or 2 and can not figure it out.

It would be greatly appreciated ?.? like the ball and score are the worst and disappear almost completely when I embed the game.

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Pong extends Applet implements MouseMotionListener, KeyListener {

int       doubleb,i,my,bx,by,px,py,compx,compy,width,height,speedx,speedy,bwidth,bheight,pwidth,pheight,score;
boolean started;
private Timer timer1;

    @Override
public void init() { 
    setSize(800,500); //setting screan size, declaring background color and some of my listeners
    width = getSize().width;
    height = getSize().height;
    setBackground(Color.black);
    pheight = 120;
    pwidth = 15;
    bheight = 30;
    bwidth = 30;
    addKeyListener(this); //listers used for the mouse and keybored input
    addMouseMotionListener(this);
    px = 35;
    compx = width - 35 - pwidth;
    newgame();
    timer1 = new Timer(10,new ActionListener() {
                @Override
        public void actionPerformed(ActionEvent e) { //momvement, physics, collusion
            height = getSize().height;
            width = getSize().width;
            bx += speedx;
            by += speedy;
            if (by <= 0 || by + bheight >= height) {
                speedy = -speedy;
            }
            if (bx <= px + pwidth && by + bheight >= py && by <= py + pheight && bx > px) {
                speedx = -speedx;
                ++score;
            }
            if (bx + bwidth >= compx && by + bheight >= compy && by <= compy + pheight && bx < compx + pwidth) {
                speedx = -speedx;
            }
            if (speedx < 0) {
                if (compy + pheight / 2 != height / 2) {
                    if (compy + pheight / 2 > height / 2) {
                        compy -= -speedx;
                    }
                    else {
                        compy += -speedx;
                    }
                }
            }
            else {
                if (by + bheight / 2 <= compy + pheight / 2) {
                    compy -= speedx;
                }
                else {
                    compy += speedx;
                }
            }
            if (compy < 0) {
                compy = 0;
            }
            if (compy + pheight > height) {
                compy = height - pheight;
            }
            if (bx + bwidth < 0) {
                py = height / 2 - pheight / 2;
                timer1.stop();
                started = false;
            }
            repaint();
        }    
    });
}

    @Override
public void mouseMoved(MouseEvent e) { 
    if (started) {
        my = e.getY();
        if (my + pheight / 2 > height) {
            my = height - pheight / 2;
        }
        if (my < pheight / 2) {
            my = pheight / 2;
        }
        py = my - pheight / 2;
        repaint();
    }
}

    @Override
public void mouseDragged(MouseEvent e) { }

    @Override
public void paint(Graphics g) {

    Font font1 = new Font("Arial", Font.BOLD, 18); //set font 
    Font font2 = new Font("Arial", Font.BOLD,40); //set font
    g.setColor(Color.white);
    g.drawRect(0,0,width - 1,height - 1);
    g.fillRect(px,py,pwidth,pheight);
    g.fillRect(compx,compy,pwidth,pheight);
    g.setFont(font1);
    g.drawString("Score: " + score,20,20); //paints the sorce 

            if (started) {
        g.fillArc(bx,by,bwidth,bheight,0,360);
    }
    else {
        g.setFont(font2); //set font
        g.setColor(Color.green); //set color
        g.drawString("Pong",width / 2 - 46,height / 2 - 16); //draws text to the screen
        g.setFont(font1);
        g.drawString("Press 's' to start",width / 2 - 69,height / 2 + 30);              
        }
    }

public void newgame() {
    py = height / 2 - pheight / 2;
    compy = py;
    bx = width / 2 - bwidth / 2;
    by = height / 2 - bheight / 2;
    speedx = 10;
    speedy = 10;
    score = 0;
}

    @Override
public void keyPressed(KeyEvent e) {
    if (e.getKeyChar() == 's') {
        started = true;
        newgame();
        timer1.start();
    }
}

    @Override
public void keyTyped(KeyEvent e) { }

    @Override
public void keyReleased(KeyEvent e) { }

}

Answer 1

you might want to look into double buffering

Basically, the issue you're having is that you clear the screen in order to redraw it. However, before the Graphics objects is completely finished updating, it gets drawn to the screen. This results in a half finished screen, and a noticeable flickering effect.

The fix to this is to instead draw your image to a seperate Graphics object first, then when it is done, swap that Graphics object with the one being displayed.

more information can be found here