How to handle ConcurrentModificationException in Android

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

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.

Unsafe usage

ArrayList<FutureTask> futureTasks;

Change with

Vector<FutureTask> futureTasks;

That's all.

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);