Need some help with dynamic object creation.

Ruzzle

Hey guys, im not really that far with processing yet so bear with me!

So I have this code:

// create an empty array for 10 MovingCircle objects
MovingCircle[] myCircleArray = new MovingCircle[10];

void setup() {
  size(400, 400);
  smooth();




}

void draw() {
     for(int i=0; i<myCircleArray.length; i++) {
    myCircleArray[i] = new MovingCircle(10,10+i*10,10);  
  }
  background(0);

  // iterate through every moving circle
  for(int i=0; i<myCircleArray.length; i++) {

    myCircleArray[i].update();
    myCircleArray[i].drawCircle();


  }


}

void mousePressed() { // if mouse pressed
println("changed");
myCircleArray = new MovingCircle[4]; //create new circles
}


class MovingCircle {

  float x;
  float y;


  float circleSize;

  MovingCircle(float xpos, float ypos, float csize) {
    x = xpos;
    y = ypos;
    circleSize = csize;
  }

  void update() {
  }


  void drawCircle() {

    fill(255);
    ellipse(x, y, circleSize, circleSize);

  }


}

Basically what is does is that it's an object based (I used an example and fitted it to my needs) script, it can generate the amount of circles I put in on the beginning at "new MovingCircle[10];"
I already moved this piece of code

for(int i=0; i<myCircleArray.length; i++) {
myCircleArray[i] = new MovingCircle(10,10+i*10,10);

from setup to draw so it can check it every time.

Im asking for help on the part at void mousePressed(), I figured out how to change the amount of objects but I want it to be one more each time I press the mouse button. Like "++".

I hope you guys understand, im not a native speaker! Thanks for the help, Ruzzle.

Chrisir

you wrote:

I already moved this piece of code from setup to draw so it can check it every time.

it really should stay in setup()...

Your question: adding elements

look at ArrayList: here you can easily add elements to your list of objects...

ArrayList<MovingCircle> myCircleArray = new ArrayList();

in setup():

    for(int i=0; i<myCircleArray.length; i++) {
        myCircleArray.add ( new MovingCircle(10,10+i*10,10) ); 
    }

in mousePressed:

 myCircleArray.add ( new MovingCircle(mouseX,mouseY,10) ); 

in draw()

  // iterate through every moving circle
  for (int i=0; i<myCircleArray.size(); i++) {

    MovingCircle myCircle = myCircleArray.get(i);
    myCircle.update();
    myCircle.drawCircle();


  }

;-)

MenteCode

In that case, you should either use a variable for the amount of circles you want, or use some trickery like this: myCircleArray = newMovingCircle[myCircleArray.length + 1];

But suppose you wanted to use a variable. Every time you clicked, you would use the increment (++) operator on the variable, and then just make the array of that size:

int arraySize = 1;
arraySize++;
myCircleArray = newMovingCircle[arraySize]; //Your array is now 2 elements long.

KevinWorkman

Why are you creating the array at the beginning of draw() each time?

This sounds like a job for an ArrayList of MovingCircles.

Ruzzle

Okay I think I understand @Chrisir (does this work here? :p) But the code still doesn't seem to work...

// create an empty array for 100 MovingCircle objects
MovingCircle[] myCircleArray = new MovingCircle[10];

void setup() {
  size(400, 400);
  smooth();

  // and actually create the objects and populate the
  // array with them

 for(int i=0; i<myCircleArray.length; i++) {
    myCircleArray.add ( new MovingCircle(10,10+i*10,10) ); 
}
}

void draw() {

  background(0);

// iterate through every moving circle
for (int i=0; i<myCircleArray.size(); i++) {

  MovingCircle myCircle = myCircleArray.get(i);
  myCircle.update();
  myCircle.drawCircle();


}

  }

void mousePressed() {
myCircleArray.add ( new MovingCircle(mouseX,mouseY,10) ); 
}


class MovingCircle {

  float x;
  float y;
  float xSpeed;
  float ySpeed;

  float circleSize;

  MovingCircle(float xpos, float ypos, float csize) {
    x = xpos;
    y = ypos;


    circleSize = csize;

  }

  void update() {
    x += xSpeed;
    y += ySpeed; 
  }


  void drawCircle() {

    fill(255);
    ellipse(x, y, circleSize, circleSize);

  }


}

It gives me the error:

Cannot invoke add (Project.MovingCircle) on the array type Project.MovingCircle[]

KevinWorkman

That's because you're mixing ArrayList code with an array.

The get() and add() functions belong to the ArrayList class. They don't work with arrays.

Use an ArrayList instead.

Chrisir

ArrayList<MovingCircle> myCircleArray = new ArrayList();

Ruzzle

Okay so I change the array MovingCircle[] myCircleArray = new MovingCircle[10];

to

ArrayList myCircleArray = new ArrayList();

?

I'm sorry im not really that far with arrays and stuff. Thanks for the help anyway!

Chrisir

yes.

Ruzzle

It doesn't work... It gives the error: myCircleArray.length cannot be resolved or is not a field

Ruzzle

Oh I get it, It was suppose to be size() not length thanks for the help

Chrisir

yeah, size()

;-)

Chrisir

see also reference

https://www.processing.org/reference/ArrayList.html

TfGuy44

And so the lesson here is, if you want to create objects dynamically, use a structure that allows for dynamic object creation!

Ruzzle

Wow thanks so much TfGuy44, unfortunately i'm not that advanced with Processing, this is however a forum for questions about processing. So if you don't like amateurs: leave.

Chrisir

Whoa, easy tiger...

TfGuy didn't want to be rude.... or sarcastic....

this is a forum for beginners and TfGuy is really helping a lot of people here....

KevinWorkman

@Ruzzle: Nobody has been rude to you. You have no reason to tell anybody to leave. People here are helping, for free, in their spare time.

I suggest you try not to be so defensive. This is a technical forum, so we don't really have time for immature flame wars.