All I want to do is create a simple Java program that has an arraylist full of objects, in this case bouncing balls, that can be added to in game. The way I want it to work is, you start the program and it is a blank screen. You press space and it creates a ball that bounces off the sides, and by pressing space it makes more balls. The problem I have is when I add more balls, it sets every item in the arraylist to the same x and y coordinates. I'm using the slick2D library, but I don't think that's the problem.
Here is the main part of the program
public static ArrayList<EntityBall> ballList;
@Override
public void init(GameContainer gc) throws SlickException {
ballList = new ArrayList<EntityBall>();
}
@Override
public void update(GameContainer gc, int delta) throws SlickException {
String TITLE = _title + " | " + gc.getFPS() + " FPS" + " | " + ballList.size() + " entities";
frame.setTitle(TITLE);
Input input = gc.getInput();
if (input.isKeyPressed(Input.KEY_SPACE)) {
addBall();
}
}
public void render(GameContainer gc, Graphics g) throws SlickException {
for(EntityBall e : ballList) {
e.render(g);
}
}
public static void addBall() {
ballList.add(new EntityBall(getRandom(0, _width - ballWidth), getRandom(0, _height - ballWidth), 20, 20));
}
public static int getRandom(int min, int max) {
return min + (int) (Math.random() * ((max - min) + 1));
}
And here is the EntityBall Class
package me.Ephyxia.Balls;
import org.newdawn.slick.Color;
import org.newdawn.slick.Graphics;
public class EntityBall {
public static int x;
public static int y;
public static int height;
public static int width;
public EntityBall(int x, int y, int width, int height) {
this.x = x;
this.y = y;
this.width = width;
this.height = height;
}
public void render(Graphics g){
g.fillOval(x, y, width, height);
}
}
The problem occurs because your instance variables x
, y
, etc. in EntityBall
are static
, meaning there is only one value of each for the entire class. Each time a new instance is created, the values are overwritten. Remove static
from the field declarations in EntityBall
, so that there are distinct values for each ball created.