Hi,

I think that this is probably a relatively simple problem, but I have searched the site and for all the trying can't seem to get my head around this.

I am relatively new to OOP but I have been working hard to understand the concepts and structure behind it!!

All I want to do is to be able to dynamically instantiate new objects as the program is running, say on a mouse click or a key pressed.  I realise that you can't add to Array objects and you have to either use a java class like vector or create a new array and copy the old one across, but I don't think I need to address this problem just yet.

how, for example, could I create a new Ball object on a key press while the program, and then run its plot and move method continually.


Ball[] balls;

void setup(){
size(400,400);
 background(0);
 smooth();
balls = new Ball[10];
for(int i=0; i< balls.length; i++)
 {
   balls[i] = new Ball(100, 100, 20);
 }
}
void draw(){
background(0);
for(int i=0; i<balls.length; i++)
{
 balls[i].plot();
 balls[i].move();
}
}
class Ball
{
 int x;
 int y;
 int r; //actually the diameter

 int xDir;
 int  xSpeed;

 Ball(int x_, int y_, int r_)
{
 this.x = x_;
 this.y = y_;
 this.r = r_;
 
 this.xDir = int(random(10));
 this.xSpeed = 1;
 }

 void plot(){
 ellipse(x,y,r,r);
 }
 void move(){
 x += (xDir * xSpeed);
 if(x > 400){
 xDir *= -1;
 }
 if(x < 0){
 xDir *= -1;
 }
}
}

This above code works fine, I just can't dynamically add balls to it!

Even if I created a blank Ball in the setup, and just didn't call the plot and move functions until a keyPressed function, I could not get this ball to behave like the others.  It appears on the screen while I am holding a key, but it doesn't move.


Thanks for any help, and I hope I have explained myself relatively clearly.  In order for this to be of any use I know I will have to use arrays to store the new Balls and this sort of thing, but I was hoping to get even half way there first!

tim