Need Help With Collision Detection

**scotthdez** · 07-24-2013, 06:56 PM

Hi im new to java and i have been making a ping pong game, to start off java, and i have run into a problem that when i run it the collision detection for rectangles doesnt always work only at certain points of it being run. Please tell me what i have done wrong with the collision detection so i can move on with java.(p.s the collision method is in the Ball.java class)

Main.java

Java Code:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JFrame;

public class Main extends JFrame implements Runnable {
	private static final long serialVersionUID = 1L;
	
	public static String title = "Ping Pong v1.0";
	public static Dimension size = new Dimension(600, 500);
	
	public static boolean running = false;
	public static boolean isOp = false;
	
	Ball ball = new Ball(startY, startY);
	Paddle p = new Paddle();
	MouseHandler mh = new MouseHandler();	
	
	Thread thread;
	
	private Image dbImage;
	private Graphics dbg;
		
	public static int startY = size.width / 2, startX = size.height / 2;
			
	public Main() {
		thread = new Thread(this, "Display");
		setPreferredSize(size);
		setMaximumSize(size);
		setMinimumSize(size);

		setTitle(title);
		pack();
		setResizable(false);
		setLocationRelativeTo(null);
		setFocusable(true);		
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBackground(Color.BLACK);
		setVisible(true);
		addKeyListener(new AL());
		addMouseListener(new MouseHandler());
		addMouseMotionListener(new MouseHandler());
		
		start();
		
	}
	
	public synchronized void start() {
		running = true;
		thread.start();
		
	}
	
	public synchronized void stop() {
		running = false;
		try {
			thread.join();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	
	@Override
	public void run() {
		try {
			while(running) {
				tick();				
				Thread.sleep(9);
			}			
		} catch(Exception e) {
			e.printStackTrace();
		}
	}
	
	public void tick() {
		ball.tick();
		p.tick();
	}
	
	public void paint(Graphics g) {
		dbImage = createImage(getWidth(), getHeight());
		dbg = dbImage.getGraphics();
		render(dbg);
		g.drawImage(dbImage, 0, 0, this);
	}

	public void render(Graphics g) {
		p.render(g);
		ball.render(g);
		
		repaint();
	}
	
	public static void main(String[] args) {
		Main main = new Main();
		
	}
	
	public class AL extends KeyAdapter {
		@Override
		public void keyPressed(KeyEvent e) {
			if (e.getKeyCode() == KeyEvent.VK_W) {
				p.setP1YDirection(-1);			
			} else if (e.getKeyCode() == KeyEvent.VK_S) {
				p.setP1YDirection(+1);
			} else if (e.getKeyCode() == KeyEvent.VK_UP) {
				p.setP2YDirection(-1);
			} else if (e.getKeyCode() == KeyEvent.VK_DOWN) {
				p.setP2YDirection(+1);
			}
			
		}
		@Override
		public void keyReleased(KeyEvent e) {
			if (e.getKeyCode() == KeyEvent.VK_W) {
				p.setP1YDirection(0);
			} else if (e.getKeyCode() == KeyEvent.VK_S) {
				p.setP1YDirection(0);
			} else if (e.getKeyCode() == KeyEvent.VK_UP) {
				p.setP2YDirection(0);
			} else if (e.getKeyCode() == KeyEvent.VK_DOWN) {
				p.setP2YDirection(0);
			}
			
		}
		
	}
	public class MouseHandler extends MouseAdapter {
				
		@Override
		public void mouseMoved(MouseEvent e) {
			int mx = e.getX();
			int my = e.getY();
			
			if (Main.isOp) {
				System.out.println("(X: " + mx + ", Y: " + my + ")");
			}
		}
		
		@Override
		public void mousePressed(MouseEvent e) {
			int mx = e.getX();
			int my = e.getY();
			
			
		}
		
	}
	
}

Ball.java

Java Code:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.util.Random;

public class Ball {
		
	Rectangle Ball;
	
	int x, y;
	int XDirection, YDirection;
	
	Paddle p = new Paddle();
	
	public Ball(int x, int y) {
		this.x = x;
		this.x = x;
		
		Ball = new Rectangle(x, y, 5, 5);
		Random r = new Random();
		int rDir = r.nextInt(1);
		if (rDir == 0) {
			rDir--;
			setXDirection(rDir);
		}
		int yDir = r.nextInt(1);
		if (yDir == 0) {
			yDir++;
			setYDirection(yDir);
		}
		
	}
	
	public void tick() {
		physics();
	}
	
	public void setXDirection(int xdir) {
		XDirection = xdir;
	}
	
	public void setYDirection(int ydir) {
		YDirection = ydir;
	}
		
	public void physics() {
		collision();
		Ball.x += XDirection;
		Ball.y += YDirection;
		
		if (Ball.x <= 0) {
			setXDirection(+1);
		}
		if (Ball.x >= 592) {
			setXDirection(-1);
		}
		if (Ball.y >= 492) {
			setYDirection(-1);
		}
		if (Ball.y <= 25) {
			setYDirection(+1);
		}
	}

	public void collision() {
		if (Ball.intersects(p.p1)) {
			setXDirection(+1);
			System.out.println("fd");
		}
		if (Ball.intersects(p.p2)) {
			setXDirection(-1);
			System.out.println("df");
		}
	}
	
	public void render(Graphics g) {
		g.setColor(Color.WHITE);
		g.fillRect(Ball.x, Ball.y, Ball.width, Ball.height);
		
	}
		
}

Paddle.java

Java Code:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;

public class Paddle {
	
	Rectangle p1 = new Rectangle(40, Main.size.width / 2 - 70, 20, 54);
	Rectangle p2 = new Rectangle(539, Main.size.width / 2 - 70, 20, 54);
	
	int P1YDirection;
	int P2YDirection;
		
	public Paddle() {
		
	}
	
	public void tick() {
		move();
	}
	
	public void move() {
		p1.y += P1YDirection;
		p2.y += P2YDirection;
		if (p1.y >= 442) {
			p1.y = 442;
		} else if (p1.y <= 25) {
			p1.y = 25;
		}
		if (p2.y >= 442) {
			p2.y = 442;
		} else if (p2.y <= 25) {
			p2.y = 25;
		}
		
	}
	
	public void setP1YDirection(int ydir) {
		P1YDirection = ydir;
	}
	
	public void setP2YDirection(int ydir) {
		P2YDirection = ydir;
	}
	
	public void render(Graphics g) {
		g.setColor(Color.BLUE);
		g.fillRect(p1.x, p1.y, p1.width, p1.height);
		g.fillRect(p2.x, p2.y, p2.width, p2.height);
	}
	
}