Circle collision detection

Question

I have created a program that drawing 2 circle on the screen and using keyboard ASWD and arrow key to move around..here is the code

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


class BallObject {
    private int x;
    private int y;
    private int radius;
BallObject() {
    x=0;
    y=0;
    radius=0;
}

BallObject (int x,int y,int radius) {
    this.x=x;
    this.y=y;
    this.radius=radius;
}
public void setX(int x) {this.x=x;}
public void setY(int y) {this.y=y;}
public void setRadius(int r) {radius=r;}

public int getX() {return x;}
public int getY() {return y;}
public int getRadius() {return radius;}

}

class Ball extends JFrame implements KeyListener {
 BallObject ball1;
 BallObject ball2;

Ball() {
    super("Simple Ball");

    setSize(800,600); //set screen resolution
    ball1 = new BallObject(getWidth()/2,getHeight()/2,20);
    ball2 = new BallObject(40,40,20);
    addKeyListener(this);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);
}

public void paint(Graphics g) {
    Graphics2D g2d = (Graphics2D)g;

    g2d.setColor(Color.BLACK);
    g2d.fill(new Rectangle(0,0,800,600));

    //drawing ball1
    g2d.setColor(Color.RED);
    g2d.fillOval(ball1.getX(),ball1.getY(),ball1.getRadius()*2,ball1.getRadius()*2);
    //drawing ball2
    g2d.setColor(Color.GREEN);
    g2d.fillOval(ball2.getX(),ball2.getY(),ball2.getRadius()*2,ball2.getRadius()*2);
}

public static void main (String args[]) {
   new Ball();
}

public void keyPressed(KeyEvent e) {
    if(e.getKeyCode()==KeyEvent.VK_LEFT)
        ball1.setX(ball1.getX()-2);

    if(e.getKeyCode()==KeyEvent.VK_RIGHT)
        ball1.setX(ball1.getX()+2);

    if(e.getKeyCode()==KeyEvent.VK_UP)
        ball1.setY(ball1.getY()-2);

    if(e.getKeyCode()==KeyEvent.VK_DOWN)
        ball1.setY(ball1.getY()+2);


    if(e.getKeyCode()==KeyEvent.VK_A){
            ball2.setX(ball2.getX()-2);
            //System.out.println("Hello");
    }


    if(e.getKeyCode()==KeyEvent.VK_D)
        ball2.setX(ball2.getX()+2);

    if(e.getKeyCode()==KeyEvent.VK_W)
        ball2.setY(ball2.getY()-2);

    if(e.getKeyCode()==KeyEvent.VK_S)
        ball2.setY(ball2.getY()+2);


        repaint();
}


            //redraw the screen to show the updated ball location
public void keyTyped(KeyEvent e) {}
public void keyReleased(KeyEvent e) {}

}

Now i need to test the collision..Once two balls are touching each other.it will show a message "COLLISION DETECTED"..pls help...

a ball is not a circle, it's an sphere and the collision formulas are different — Adrián, Feb 03 '13 at 14:48
Also you should override `paintComponent` , not `paint` in swing apps. — Extreme Coders, Feb 03 '13 at 14:51
Check this answer http://stackoverflow.com/questions/345838/ball-to-ball-collision-detection-and-handling — Adrián, Feb 03 '13 at 14:53

score 2 · Answer 1 · answered Feb 03 '13 at 14:48

2

Isn't it simply: if the distance of both center points is less or equal to the sum of the radiuses, then there is a collision?

answered Feb 03 '13 at 14:48

Dan

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@OngPek If you wrote this code yourself, then you can very well calculate the distance between two points and do a comparison. We cannot write your code for you. – mostruash Feb 03 '13 at 14:52
@OngPek Just very simple logical or math operations. – shuangwhywhy Feb 03 '13 at 14:54
This coding is my lecturer gave me..he asked me to add collision detection function into it..he just taught me the formula for the collision detection..i do not know how to add into it =( – Ong Pek Feb 03 '13 at 14:54
I knw the formula to calculate..but i do not know how to apply into java.....pls help =( – Ong Pek Feb 03 '13 at 15:00

Circle collision detection

1 Answers1