java - 当 Sprite 位于特定位置时，如何将其移除？

Question

我的 Sprite 是在随机时间生成的，生成后会向上移动，直到它们到达某个位置，然后它们应该被删除。这就是我一直在尝试做的事情，但我总是收到错误。

//this method is called at random time
 public void newEnemy(){
        Sprite enemy= Pools.obtain(Sprite.class);
        enemy.set(enemySpr);
        enemy.setPosition(200,150);
        enemies.add(enemy);
    }



//removing the enemy
 while (enemyIterator.hasNext()){
  Sprite nextEnemy=enemyIterator.next();//<--error here,this is line 66  
           if(enemySpr.getY()+enemySpr.getHeight()>=treeObj.treeSpr.getY()){
               removeEnemy(nextEnemy);
           }
       }



//removeEnemy method
public void removeEnemy(Sprite sprite){
        enemies.remove(sprite);
        Pools.free(sprite);
    }



//this is the error there I get:

Exception in thread "LWJGL Application" java.util.ConcurrentModificationException
   at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
   at java.util.ArrayList$Itr.next(ArrayList.java:851)
   at com.dreamroad.savethetree.EnemyClass.update(EnemyClass.java:66)
   at com.dreamroad.savethetree.MyGdxGame.render(MyGdxGame.java:51)
   at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:215)
   at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:120)

Process finished with exit code 0

我认为这就是我收到错误的原因，但我不确定:

public void draw(SpriteBatch batch){
        for(Sprite drawEnemy:enemies) {    //enemies is the ArrayList
            drawEnemy.draw(batch);
            drawEnemy.translateY(deltaTime * movement);
        }
    }

Answer 1

正如 Subler 所说，这里的问题是你试图在迭代列表的同时从列表中删除某些内容。

但是，有一个更简单的解决方案。只需在迭代器上调用remove()即可。这将删除迭代器的当前元素。

//removing the enemy
while (enemyIterator.hasNext()) {

    Sprite nextEnemy = enemyIterator.next();
    if(enemySpr.getY() + enemySpr.getHeight() >= treeObj.treeSpr.getY()) {
        enemyIterator.remove();
        Pools.free(nextEnemy);
    }
}