Question

I’m creating an applet in which a sheep is herded by a dog, both are objects as the dog object moves closer the sheep the sheep moves away in a random direction. (I’m sorry I know I’ve asked a lot of questions about this applet). So far everything works except the sheep object wont stay within the bounds I’ve set and eventually disappears off the screen entirely. I’ve tried lots of different things but nothing seems to work. Any ideas why the sheep object wont stay within the bounds? Any help would be much appreciated.
Here is the code, there are two separate java files:

MainPanel.java

import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.Random;


import javax.swing.JPanel;

public class MainPanel extends JPanel implements MouseMotionListener
{

    private static final long serialVersionUID = 1L;
    Dog dog;
    Sheep sheep;
    int[] directionNumbersLeft = {0, 1, 3};
    int[] directionNumbersRight = {1, 2, 3};
    int[] directionNumbersUp = {0, 1, 2};
    int[] directionNumbersDown = {0, 2, 3};
    int x;
    int selection;
    int xposR;
    int yposR;
    int sheepx;
    int sheepy;
    int sheepBoundsx;
    int sheepBoundsy;
    int MAX_DISTANCE = 50;
    int direction;
    int distance;

    public MainPanel()
    {

        addMouseMotionListener(this);
        sheepx = 175;
        sheepy = 75;
        dog = new Dog(22,22);
        sheep = new Sheep(sheepx, sheepy);
        sheepBoundsx = 30;
        sheepBoundsy = 30;



    }


    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        dog.display(g);
        sheep.display(g);
        g.drawRect(20, 20, 600, 600);
    }



    public void mouseDragged(MouseEvent e)
    {
        xposR = e.getX();
        yposR = e.getY();
        dog.setLocation(xposR, yposR);
        sheep.setLocation(sheepx, sheepy);
        direction = (int)(Math.random()*4);
        Random rand = new Random();
        x = rand.nextInt(3);

        if (xposR > sheepx&& xposR < sheepx+sheepBoundsx && yposR > sheepy
                && yposR < sheepy+sheepBoundsy && direction == 0){
            sheepx = sheepx + 50;
        }
        if (xposR > sheepx&& xposR < sheepx+sheepBoundsx && yposR > sheepy
                && yposR < sheepy+sheepBoundsy && direction == 1){
            sheepy = sheepy + 50;
        }

        if (xposR > sheepx&& xposR < sheepx+sheepBoundsx && yposR > sheepy
                && yposR < sheepy+sheepBoundsy && direction == 2){
            sheepx = sheepx - 50;
        }

        if (xposR > sheepx&& xposR < sheepx+sheepBoundsx && yposR > sheepy
                && yposR < sheepy+sheepBoundsy && direction == 3){
            sheepy = sheepy - 50;
        }
        if (sheepx <= 20){
            direction = directionNumbersLeft[x];
        }
        if (sheepy <= 20){
            direction = directionNumbersUp[x];
        }
        if (sheepx >= 600){
            direction = directionNumbersRight[x];
        }
        if (sheepy >= 600){
            direction = directionNumbersDown[x];
        }
        if (xposR < sheepx){
            direction = directionNumbersLeft[x];
        }
        if (xposR > sheepx){
            direction = directionNumbersRight[x];
        }
        if (yposR > sheepy){
            direction = directionNumbersDown[x];
        }
        if (yposR < sheepy){
            direction = directionNumbersUp[x];
        }


        repaint();
    }



    public void mouseMoved(MouseEvent e) {


    }



}

SheepDog.java

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


import javax.swing.*;


public class SheepDog extends JApplet
{
    /**
     *
     */
    private static final long serialVersionUID = 1L;
    /**
     *
     */


    MainPanel mainPanel;



    public void init()
    {
        mainPanel = new MainPanel();
        add(mainPanel);


    }




}
class Dog
{
    int xpos;
    int ypos;
    int circleWidth = 30;
    int circleHeight = 30;

    public Dog(int x, int y)
    {
        xpos = x;
        ypos = y;

    }

    public void setLocation(int lx, int ly)
    {
        xpos = lx;
        ypos = ly;
    }

    public void display(Graphics g)
    {
        g.setColor(Color.blue);
        g.fillOval(xpos, ypos, circleWidth, circleHeight);
    }
}

class Sheep
{
    int xpos;
    int ypos;
    int circleWidth = 30;
    int circleHeight = 30;

    public Sheep(int x, int y)
    {
        xpos = x;
        ypos = y;

    }

    public void setLocation(int lx, int ly)
    {
        xpos = lx;
        ypos = ly;
    }

    public void display(Graphics g)
    {
        g.setColor(Color.green);
        g.fillOval(xpos , ypos, circleWidth, circleHeight);
        g.drawOval(xpos - 10, ypos - 10, 50, 50);
    }


}

Answer 1

Try adding elses to your long string of if() statements, like so:

    if (sheepx <= 20){
        direction = directionNumbersLeft[x];
    } else if (sheepy <= 20){
        direction = directionNumbersUp[x];
    } else if (sheepx >= 600){
        direction = directionNumbersRight[x];
    } else ...

The way you had it before, if sheepx was left then 20, and less than the dog’s x, it would still go away from the dog, even though it should’ve been worried about the boundaries. This was because both if statements would trigger, and modify direction, but since you check’d for boundary first, that would be overwritten by the attempt to run from the dog. Try this solution, tell me how it works