Pacman issue with walls

**mightyking** · November 25th, 2011, 12:42 PM

Hi guys, so I've been making this java program to simulate a rather simple pacman, I've been doing fine until I reached the point where I can't figure out how to put a restriction on the pacman so he doesn't walk thru a wall. Here is my source code:

Background.png pacman.jpg

import javax.swing.JFrame;
 
public class Pac {
    public static void main(String args[]){ 
        Pacman p = new Pacman();
        JFrame f = new JFrame();
        f.add(p);
        f.setVisible(true);
        f.setSize(180, 258);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setTitle("Pacman");
    }
}

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
 
public class Pacman extends JPanel implements ActionListener, KeyListener {
 
    Timer t = new Timer(5, this);
    int x = 75, y = 80, velX = 0, velY = 0;
    private BufferedImage sheet;
    private BufferedImage sheet1;
    private int frame;
 
    public Pacman() {
        t.start();
        addKeyListener(this);
        setFocusable(true);
        setFocusTraversalKeysEnabled(false);
    }
 
    @Override
    public void paintComponent(Graphics g) {
        try {
            sheet = ImageIO.read(Pacman.class.getResource("/images/Background.png"));
        } catch (IOException ex) {
            Logger.getLogger(Pacman.class.getName()).log(Level.SEVERE, null, ex);
        }
        try {
            sheet1 = ImageIO.read(Pacman.class.getResource("/images/pacman.png"));
        } catch (IOException ex) {
            Logger.getLogger(Pacman.class.getName()).log(Level.SEVERE, null, ex);
        }
        if (sheet != null) {
            g.drawImage(sheet, 0, 0, null);
        }
        g.drawImage(sheet1.getSubimage(629 + (frame / 3) * (15 + 2), 51, 15, 15), x, y, null);
 
        Graphics2D g2 = (Graphics2D) g;
        g2.setColor(Color.GREEN);
        g2.fillRect(66, 98, 32, 24);
    }
 
    @Override
    public void actionPerformed(ActionEvent e) {
        repaint();
        if (x < 7 || x > 143) {
            velX = 0;
        }
        if (y < 8 || y > 199) {
            velY = 0;
        }
 
        x += velX;
        y += velY;
    }
 
    public void up() {
        if (y > 199) {
            y = 199;
        }
        velY = -5;
        velX = 0;
    }
 
    public void down() {
        if (y < 8) {
            y = 8;
        }
        velY = 5;
        velX = 0;
    }
 
    public void left() {
        if (x > 143) {
            x = 143;
        }
        velX = -5;
        velY = 0;
    }
 
    public void right() {
        if (x < 7) {
            x = 7;
        }
        velX = 5;
        velY = 0;
    }
 
    public void walls() {
 
    }
 
    @Override
    public void keyPressed(KeyEvent e) {
 
        int code = e.getKeyCode();
        if (code == KeyEvent.VK_UP) {
            up();
        }
        if (code == KeyEvent.VK_DOWN) {
            down();
        }
        if (code == KeyEvent.VK_RIGHT) {
            right();
        }
        if (code == KeyEvent.VK_LEFT) {
            left();
        }
    }
 
    @Override
    public void keyTyped(KeyEvent e) {
    }
 
    @Override
    public void keyReleased(KeyEvent e) {
    }
}

I would like to get some help to figure out how to avoid the pacman from entering a wall. I have drawn a rectangle but how do I declare that the pacman's speed should change to O "velX=0 or velY=0" when it touches the wall?

Say for the following rectangle

g2.setColor(Color.GREEN);
g2.fillRect(66, 98, 32, 24);

what could I do in the method

public void walls () {}

**Tjstretch** · November 25th, 2011, 12:47 PM

Take a glance at the methods in Component (Which JFrame extends) Especially getSize. Then look at Dimension if you do not know about it. Note that the left wall has an x of 0 and the top wall has a y of 0.

Component (Java Platform SE 7 )
Dimension (Java Platform SE 7 )

**KevinWorkman** · November 25th, 2011, 12:48 PM

Before you increment your pacman's position, check to see whether that position is in a wall. If it is, set the speed to zero.

**mightyking** · November 25th, 2011, 12:52 PM

I already have the outside wall limits completed, and it stops accordingly

public void actionPerformed(ActionEvent e) {
        repaint();
        if (x < 7 || x > 143) {
            velX = 0;
        }
        if (y < 8 || y > 199) {
            velY = 0;
        }
 
        x += velX;
        y += velY;
    }

however when I try to use the same type of code for a rectangle that is inside the outer walls, it doesn't work the same way.

**mightyking** · November 25th, 2011, 12:53 PM

Originally Posted by KevinWorkman

Before you increment your pacman's position, check to see whether that position is in a wall. If it is, set the speed to zero.

I have no idea how to go about doing that, I would guess that would go into the keyPressed method right?

**KevinWorkman** · November 25th, 2011, 12:59 PM

Originally Posted by mightyking

I have no idea how to go about doing that, I would guess that would go into the keyPressed method right?

Eh, I suppose that's one way to do it. It's probably not the best way, but it's a simple start. But yeah, it would go wherever your logic for moving your pacman character is.

I suggest you get out a piece of graph paper and draw a sample pacman maze. Write down the coordinates and sizes of each inner wall, and see if you can figure out a formula that determines whether a point is inside each wall.

**mightyking** · November 25th, 2011, 01:56 PM

Logic-wise im aware of what I need to do, but programing-wise I'm completely off track. Any aid?

I've been trying and trying but none make any good progress

**mightyking** · November 25th, 2011, 02:41 PM

I tried to change my actionPerformed method to this:

@Override
    public void actionPerformed(ActionEvent e) {
        repaint();
// sets the limits of the outer walls and changes the pacmans velocity to 0 so it will stop.
        if (x < 7 || x > 143) {
            velX = 0;
        }
 
        if (y < 8 || y > 199) {
            velY = 0;
        }
 
        // attempt at making the center inner wall's limits so the pacmans velocity will change to 0
        for(x=66; x<98; x++){
            velX=0;
            for(y=98; y<122; y++)
                velY=0;
        } 
 
        x += velX;
        y += velY;
    }

however here, i don't see why it doesnt work, just makes my pacman stay still in one position, why? pacmanstuck.png

        // attempt at making the center inner wall's limits so the pacmans velocity will change to 0
        for(x=66; x<98; x++){
            velX=0;
            for(y=98; y<122; y++)
                velY=0;
        }

**KevinWorkman** · November 26th, 2011, 01:03 PM

I am really not sure what you're expecting that for loop to do. You should check pacman's position against the walls with some if statements, not a for loop.

**mightyking** · November 27th, 2011, 07:58 PM

I got it working by the following method:

@Override
    public void actionPerformed(ActionEvent e) {
        repaint();
 
        //Pacman 
        if (x == 3 || x == 146) {
            velX = 0;
        }
        if (y == 3 || y == 202) {
            velY = 0;
        }
        //up
        if (((x >= 100 && x <= 145) || (x >= 4 && x <= 49)) && y == 76) {
            velY=0;
        }
        if (((x >= 100 && x <= 145) || (x >= 4 && x <= 49)) && y == 201) {
            velY=0;
        }
        if ((x >= 51 && x <= 98 ) && y == 76) {
            velY=0;
        }
        if ((x >= 51 && x <= 98 ) && y == 122) {
            velY=0;
        }
        if ((x >= 51 && x <= 98 ) && y == 170) {
            velY=0;
        }
        //down
        if (((x >= 100 && x <= 145) || (x >= 4 && x <= 49)) && y == 5) {
            velY=0;
        }
        if (((x >= 100 && x <= 145) || (x >= 4 && x <= 49)) && y == 131) {
            velY=0;
        }
        if ((x >= 51 && x <= 98 ) && y == 35) {
            velY = 0;
        }
        if ((x >= 51 && x <= 98 ) && y == 83) {
            velY = 0;
        }
        if ((x >= 51 && x <= 98 ) && y == 131) {
            velY = 0;
        }
        //left
        if (((y >= 5 && y <= 76) || (y >= 146 && y <= 201)) && x == 49) {
            velX = 0;
        }
        if (((y >= 5 && y <= 76) || (y >= 146 && y <= 201)) && x == 145) {
            velX = 0;
        }
        if ((y >= 35 && y <= 74 ) && x == 98) {
            velX = 0;
        }
        if ((y >= 83 && y <= 122 ) && x == 98) {
            velX = 0;
        }
        if ((y >= 131 && y <= 170 ) && x == 98) {
            velX = 0;
        }
        //right
        if (((y >= 5 && y <= 76) || (y >= 146 && y <= 200)) && x == 4) {
            velX = 0;
        }
        if (((y >= 5 && y <= 76) || (y >= 146 && y <= 200)) && x == 100) {
            velX = 0;
        }
        if ((y >= 35 && y <= 74 ) && x == 51) {
            velX = 0;
        }
        if ((y >= 83 && y <= 122 ) && x == 51) {
            velX = 0;
        }
        if ((y >= 131 && y <= 170 ) && x == 51) {
            velX = 0;
        }
 
        x += velX;
        y += velY;
    }
 
    public void up() {
        if (y == 202) {
            y = 201;
        }
        if(y == 131){
            y = 130;
        }
        if(y==35){
            y=34;
        }
        if(y==83){
            y=82;
        }
 
        if (((x >= 100 && x <= 145) || (x >= 4 && x <= 49)) && y == 76) {
            y = 77;
        }
        if (((x >= 100 && x <= 145) || (x >= 4 && x <= 49)) && y == 201) {
            y = 202;
        }
 
        if ((x >= 51 && x <= 98 ) && y == 76) {
            y = 77;
        }
        if ((x >= 51 && x <= 98 ) && y == 122) {
            y=123;
        }
        if ((x >= 51 && x <= 98 ) && y == 170) {
            y=171;
        }
 
        velY = -1;
        velX = 0;
    }
 
    public void down() {
        if (y == 3) {
            y = 4;
        }
        if(y==76){
            y=77;
        }
        if(y==122){
            y=123;
        }
        if(y==170){
            y=171;
        }
        if (((x >= 99 && x <= 144) || (x >= 3 && x <= 50)) && y == 5) {
            y = 4;
        }
        if (((x >= 99 && x <= 144) || (x >= 3 && x <= 50)) && y == 131) {
            y = 130;
        }
        if ((x >= 51 && x <= 98 ) && y == 35) {
            y = 34;
        }
        if ((x >= 51 && x <= 98 ) && y == 83) {
            y = 82;
        }
        if ((x >= 51 && x <= 98 ) && y == 131) {
            y = 130;
        }
        velY = 1;
        velX = 0;
    }
 
    public void left() {
        if (x == 146) {
            x = 145;
        }
        if(x==4){
            x=3;
        }
        if(x==51){
            x=50;
        }
        if(x==100){
            x=99;
        }
        if (((y >= 5 && y <= 76) || (y >= 146 && y <= 201)) && x == 49) {
            x = 50;
        }
        if (((y >= 5 && y <= 76) || (y >= 146 && y <= 201)) && x == 145) {
            x = 146;
        }
        if ((y >= 35 && y <= 74 ) && x == 98) {
            x = 99;
        }
        if ((y >= 83 && y <= 122 ) && x == 98) {
            x = 99;
        }
        if ((y >= 131 && y <= 170 ) && x == 98) {
            x = 99;
        }
 
        velX = -1;
        velY = 0;
    }
 
    public void right() {
        if (x == 3) {
            x = 4;
        }
        if(x==49){
            x=50;
        }
        if(x==98){
            x=99;
        }
        if(x==145){
            x=146;
        }
 
        if (((y >= 5 && y <= 76) || (y >= 146 && y <= 200)) && x == 4) {
            x = 3;
        }
        if (((y >= 5 && y <= 76) || (y >= 146 && y <= 200)) && x == 100) {
            x = 99;
        }
        if ((y >= 35 && y <= 74 ) && x == 51) {
            x = 50;
        }
        if ((y >= 83 && y <= 122 ) && x == 51) {
            x = 50;
        }
        if ((y >= 131 && y <= 170 ) && x == 51) {
            x = 50;
        }
 
        velX = 1;
        velY = 0;
    }

**Junky** · November 27th, 2011, 08:40 PM

Gaaaaaah!

Why not hava a collection of Wall objects. Then you loop over them checking to see if Pacman's co-ords are inside any of the walls. That way your code will not change should you change maps.

**mightyking** · November 30th, 2011, 02:21 PM

Originally Posted by Junky

Gaaaaaah!

Why not hava a collection of Wall objects. Then you loop over them checking to see if Pacman's co-ords are inside any of the walls. That way your code will not change should you change maps.

Yes I know this is hardly the most efficient way, but at least for now I got a working pacman

I will however strive to work it out much better so I could, as you say change the maps to my liking without having to change the code and all the coordinates.

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