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## Java Collision Detection Help

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### #1Gearslayer360  Members

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Posted 25 July 2012 - 08:24 PM

I copied the code from Eclipse because the adding it seemed to cut it off after 60 lines. I can fix it if you tell me how and you want it in the special box. Anyways this is the enemy class in my game. Currently what I have is a little tank that moves and shoots bullets at an enemy(moving square). When he shoots the enemy health decreases, it reverses the enemy direction and the score goes up by 100. My problem is basically that the collision detection seems to be random...Sometimes it will count the bullet as 1 hit...sometimes 2 or 3. I don't know why it's doing this. Can anyone help or give suggestions? All help appreciated. Thank you.

package game;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.util.Random;
public class Enemy implements Runnable
{
int x;
int y;
int xDirection;
int yDirection;
int health;
int p1Score;

Player p1 = new Player(290, 15, 10);
Rectangle enemy;

public Enemy(int x, int y, int health)
{
p1Score = 0;
this.x = x;
this.y = y;
this.health = health;

Random r = new Random();
int rDir = r.nextInt(1);

if(rDir == 0)
{
rDir--;
setXDirection(rDir);
}

int yrDir = r.nextInt(1);

if(yrDir == 0)
{
yrDir--;
setYDirection(yrDir);
}

enemy = new Rectangle(this.x, this.y, 30, 30);
}

public void setXDirection(int direction) {
xDirection = direction;
}
public void setYDirection(int direction) {
yDirection = direction;
}

public void draw(Graphics g)
{
//draw the enemy initially
g.setColor(Color.white);
g.fillRect(enemy.x, enemy.y, enemy.width, enemy.height);

//if the enemy dies remove it
//Need to delete the current one and make a new enemy
if(health <= 0)
{
g.clearRect(enemy.x, enemy.y, enemy.width, enemy.height);
}
}

public void collision()
{
//Checks first if the player bullet is null
//Collision between the bullet and the player.
//Checks if the bounds of bullet and enemy intersect

if(p1.bullet != null && enemy.getBounds().contains(p1.bullet.getBounds()))
{
setYDirection(-1);
p1Score+=100;
health-=1;
}

}

public void move()
{
//enemy.x+=xDirection;
enemy.y+=yDirection;

//Checks if the enemy hits the left side of the screen
//if so reverse the direction to the right
if(enemy.x <= 0)
{
setXDirection(1);
}

//Checks if the enemy hits the right side of the screen
//if so reverse the direction to the left
if(enemy.x >= 780)
{
setXDirection(-1);
p1Score++;
}

//Checks if the enemy hits the top of the screen
//if so reverse the direction to the bottom
if(enemy.y <= 30)
{
setYDirection(1);

}

//Checks if the enemy hits the bottom of the screen
//if so reverse the direction to the top
if(enemy.y >= 570)
{
setYDirection(-1);

}
//collision();

}

public void run()
{
try
{
while(true)
{
move();
collision();
}
}
catch(Exception e){System.err.println(e.getMessage());}
}

public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
public int getHealth() {
return health;
}
public void setHealth(int health) {
this.health = health;
}
public int getP1Score() {
return p1Score;
}
public void setP1Score(int score) {
p1Score = score;
}
public Player getP1() {
return p1;
}
public void setP1(Player p1) {
this.p1 = p1;
}
public Rectangle getEnemy() {
return enemy;
}
public void setEnemy(Rectangle enemy) {
this.enemy = enemy;
}
public int getXDirection() {
return xDirection;
}
public int getYDirection() {
return yDirection;
}

}

Edited by Gearslayer360, 25 July 2012 - 08:27 PM.

### #2serumas  Members

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Posted 26 July 2012 - 03:04 AM

perhaps yuo dont erase bullet imediately afer hiting something...
From this code just whis idea comes...

### #3Gearslayer360  Members

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Posted 26 July 2012 - 03:44 PM

Ah you could be right. I could probably do that but I don't know how to destroy it. I have looked on the internet but I haven't really found any good information. Any suggestions on how to do it?

### #4Gearslayer360  Members

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Posted 26 July 2012 - 04:40 PM

Thank you for the suggestion. I found a way to implement the destroying of the bullet upon impact. It now works correctly.

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