从arraylist android中删除

Question

I have an android game which involves a ship shooting enemies. I am trying to make it so that if the enemies are within a certain distance of the ammos, then the enemys remove themselves from the screen. I have attempted to do it and the code compiles, but i am unsure why the enemys arent being removed from the screen once been hit. Can anyone see anything wrong with the code below? Thankyou

for (TopEnemy i : newTopEnemy)
{
    for (int q = 0; q < ammo.length; q++)
    {
       float xsubs = i.enemyX - ammo[q].positionX;
       float ysubs = i.enemyY - ammo[q].positionY;
       float squared = (xsubs * xsubs) + (ysubs * ysubs);
       float distance = (float)Math.sqrt(squared);
       if (distance < 10.0)
       {
          newTopEnemy.remove(q);
       }
    }
 }  

Answer 1

Shouldn't it be newTopEnemy.remove(i); ? q looks like an index on ammo .

Answer 2

You need to use Iteratore.remove .

for (Iterator<TopEnemy> itr = intList2.iterator(); iterator.hasNext();) {
    TopEnemy enemy = itr.next();
    //code here 
    if (distance < 10.0) {
            itr.remove();
    }
}

Answer 3

You cannot remove from a list while using the foreach loop. You have to use an iterator to loop through the list and then remove using the remove method.

Answer 4

I would add to Vlad answer that is not always a good ideea to remove an item while looping over a list like that. I would do it like this :

for (int i = newTopEnemy.size()-1;i>=0;i--) {
    TopEnemy enemy = newTopEnemy.get(i);
    for (int q = 0; q < ammo.length; q++) {
        float xsubs = enemy.enemyX - ammo[q].positionX;
        float ysubs = enemy.enemyY - ammo[q].positionY;
        float squared = (xsubs * xsubs) + (ysubs * ysubs);
        float distance = (float)Math.sqrt(squared);
        if (distance < 10.0) {
            newTopEnemy.remove(i);
            break;
        }
    }
}