How to handle ConcurrentModificationException in Android

Im trying to delete item from a ArrayList. Some times it pops an exception, "java.util.ConcurrentModificationException".

First i tried to remove them by array_list_name.remove(i), but it failed and some people were asked to use Iterator instead. So my current code is as follows.

for (Iterator<Collectable> iter = array_list_name.iterator(); iter.hasNext();) {
   Collectable s = iter.next();
   if (s.equals(array_list_name.get(id))){
       iter.remove();
       return true;
   }
}

And i call "array_list_name" inside onDraw() function in view. my view is a SurfaceView. Can any one suggest me how to delete items from ArrayList without getting this error.

Murat Can ALPAY

Try using java.util.concurrent.CopyOnWriteArrayList instead of ArrayList

Seems from the comments that your ArrayList<Collectable> is accessed from the onDraw() method in one thread, by the UI, concurrently with you removing items from it in another thread.

So, why not just wrap both accessors in a

synchronized(array_list_name)
{
    // UI access code or item removal code
}

Note that this might make your UI laggy if removing items takes a long time. If this is the case, consider making a list of all item indexes to be removed, and remove them in a tight synchronized loop after iterating over the whole list.

Update

It seems to me your whole code snippet could be simplified to just:

synchronized(array_list_name)
    return array_list_name.remove(id);

You could create a defensive copy of the list like so:

List copy = new ArrayList(array_list_name);
for (Iterator<Collectable> iter = copy.iterator(); iter.hasNext();) {
   Collectable s = iter.next();
   if (s.equals(copy.get(id))){
       iter.remove();
       return true;
   }
}

Have you ever thought to use Vector List ? If you need a thread-safe implementation, you should use Vector instead of ArrayList. Vector list's usage is same with ArrayList. Just change its type with Vector.