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  LibGdx, update list while iterating through it  (Read 9337 times)
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Offline vastrolorde

Junior Devvie





« Posted 2014-07-07 13:57:49 »

IS there a way to add and delete elements from a ArrayList while im iterateing through it ? Or is there some other Array Type for it?
Offline Gibbo3771

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« Reply #1 - Posted 2014-07-07 14:04:09 »

ehhhh...


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    for(Thing thing: aListOfThings){
        thing.update();
        if(thing.hasDoneSomethingBad)
            aListOfThings.remove(thing, true);
}


Unless I am missing something here?

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Offline BurntPizza

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« Reply #2 - Posted 2014-07-07 14:07:03 »

@Gibbo If I'm not mistaken, that'll throw a ConcurrentModificationException

@OP: http://www.java-gaming.org/topics/concurrentmodificationexception-when-removing-an-item-from-an-arraylist/32939/view.html
A few solutions here, an iterator is probably the most fool-proof.
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Offline vastrolorde

Junior Devvie





« Reply #3 - Posted 2014-07-07 16:41:38 »

This works for removing. What about adding. IM iterating through my Array of Entities, and at one point entity must add ned entitis to the list. On the moment of addition i get the error. Array is static and the addition happen in another class.
Offline Gibbo3771

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« Reply #4 - Posted 2014-07-07 17:22:03 »

@Gibbo If I'm not mistaken, that'll throw a ConcurrentModificationException

Hmmm, does not seem to with LibGDX Array.

For instance in my breakout game I am iterating through the Array of Blocks, to check if Ball overlaps a Block, if so remove from array. It gets removed during iteration.

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Offline PandaMoniumHUN

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White-bearded OGL wizard


« Reply #5 - Posted 2014-07-07 19:30:21 »

Hmmm, does not seem to with LibGDX Array.
That's because LibGDX's developers took care if this issue, but with Java's built-in collections you can not modify a collection while you're iterating over it using a for-each loop.

To the OP: Use ListIterators. They can both remove and add elements to the collection during iteration. Smiley

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Offline vastrolorde

Junior Devvie





« Reply #6 - Posted 2014-07-08 06:21:18 »

I have it setup like this, and im still gettign the error message. These 2 codes are in different classes.

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       ListIterator<Entity> iter = entitys.listIterator();
       while(iter.hasNext()){
          Entity e = iter.next();
          e.update(delta);
          if(!e.onScreen()){
             iter.remove();
          }
       }


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public class Shoot {
   
   public Shoot(float x, float y){
      GameWorld.entitys.add(new CircleBullet(x,y, 0, 10));
      GameWorld.entitys.add(new CircleBullet(x,y, 5, 10));
   }
}
Offline Gibbo3771

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« Reply #7 - Posted 2014-07-08 08:50:29 »

Hmmm, does not seem to with LibGDX Array.
That's because LibGDX's developers took care if this issue, but with Java's built-in collections you can not modify a collection while you're iterating over it using a for-each loop.

To the OP: Use ListIterators. They can both remove and add elements to the collection during iteration. Smiley

So why is the OP using an ArrayList and not an Array<?>....


"This code works flawlessly first time and exactly how I wanted it"
Said no programmer ever
Offline vastrolorde

Junior Devvie





« Reply #8 - Posted 2014-07-08 09:17:39 »

Problem solved. Using Array worked. Just asking, is there a better way to fill an array in other class other than declaring it static?
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