Understanding element.remove [SOLVED]

superted89

Understanding element.remove [SOLVED]

in Contributed Library Questions • 3 months ago

I am having trouble getting this to work. I want to add drops when an accelerometer is titled and remove drops when it returns to normal. Where am I going wrong? Thanks.

import maxlink.*;

ArrayList<Rain> drops;
int r = 60;
public float a;

MaxLink link = new MaxLink(this, "bouncer");

void setup()
{
size(600,600);
noStroke();
frameRate(30);
smooth();
drops = new ArrayList<Rain>();
drops.add(new Rain());
link.declareInlet("a");
}

void draw()
{
background(255);
for (int i = drops.size()-1; i >=0; i--){
    Rain rain = drops.get(i);
    rain.fall();}


    if (a > 23.){
      drops.add(new Rain());
    }

     if (a < 23.){
          drops.remove(new Rain());
        }
      }

Replies(4)

GoToLoop

Re: Why wont it work!! item.remove

3 months ago

We have no idea either! Since we dunno where variable a changes its value!

However, instruction new is used to instantiate new objects out of a class, not to remove them!

Here's a shorter version of your draw() section:

void draw() {
  background(-1);

  for ( int i = drops.size(); i-- != 0; drops.get(i).fall() );

  if (a > 23.)        drops.add( new Rain() );
  else if (a < 23.)   drops.remove(0);
}

There are 3 situations there:

if a > 23, keeps adding drops like there's a heavy storm going on.
if a < 23, keeps removing drops, even though it may come a time there's no more to dry off.
if a = 23, do nothing.

In an ArrayList, its method add() puts a new element at its end or "tail".

If you want to remove the oldest element of it, you go to index 0, which is its "head"! That is -> remove(0).

But take notice it's the slowest action to take upon an ArrayList!

amnon.owed

Re: Why wont it work!! item.remove

3 months ago

You create a new object. Then you search the list for that object to be removed. By definition it won't be found, because it's not on the list. So that line basically does a whole lot of nothing. Either remove an object via it's index or an actual reference to the object.

See: http://docs.oracle.com/javase/6/docs/api/java/util/ArrayList.html

Also see: https://forum.processing.org/topic/where-to-place-threads-and-other-forum-practices

Take note that programming questions is only for questions that do not require hardware or libraries.

Haven't moved this thread, because your code is not runnable anyway.

superted89

Re: Why wont it work!! item.remove

3 months ago

Thank you for your help I know have it working. Here is the runnable code without additional libraries or hardware.

ArrayList<Rain> drops;
public float a;

void setup()
{
size(600, 600);
noStroke();
frameRate(30);
smooth();
drops = new ArrayList<Rain>();
drops.add(new Rain());
}

void draw()
{
background(255);
for (int i = drops.size()-1; i >=0; i--) {
    Rain rain = drops.get(i);
    rain.fall();
}
}

void mousePressed() {
drops.add(new Rain());
}

class Rain {
float r =random(600);
float y = 0;
int x = 0;
float speed;

void fall() {
    y=y+7;
    frameRate(60);

    fill(0, 10, 200, 200);
    ellipse(r, y, 10, 10);

    if (y> height) {
      r = random(600);
      y = 0;

      drops.remove(0);
    }
}
}