我正在尝试构建一款太空入侵者游戏,并开发了这一段代码,以使所有外星人在其中一个击中屏幕边缘时都会掉落,但是当它发生时,我收到了一条看起来非常令人讨厌的错误消息命中Enemy de = DownIterator.next();
行。游戏仍然按预期运行,但当它到达该行时,它会在后台触发这些错误消息。
代码如下:
Iterator<Enemy> iterator = enemyList.iterator();
while (iterator.hasNext()) {
Enemy e = iterator.next();
if(e!=null && e.isActive()){
e.move();
e.draw(g);
if(e.edgeHit()){
Iterator<Enemy> downwardIterator = enemyList.iterator();
while (iterator.hasNext()) {
Enemy de = downwardIterator.next();
de.dropPosition();
de.changeDirection();
}
}
}
else{
iterator.remove();
}
}
e.move只是让敌人左右移动。 e.edgeHit 检测任何敌人何时到达游戏屏幕的边缘。
这是到达该行时的完整跟踪:
Exception in thread "AWT-EventQueue-0" java.util.NoSuchElementException
at java.util.ArrayList$Itr.next(ArrayList.java:834)
at GamePanel.paintComponent(GamePanel.java:96)
at javax.swing.JComponent.paint(JComponent.java:1054)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5219)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1529)
at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1452)
at javax.swing.RepaintManager.paint(RepaintManager.java:1249)
at javax.swing.JComponent._paintImmediately(JComponent.java:5167)
at javax.swing.JComponent.paintImmediately(JComponent.java:4978)
at javax.swing.RepaintManager$3.run(RepaintManager.java:808)
at javax.swing.RepaintManager$3.run(RepaintManager.java:796)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:769)
at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:718)
at javax.swing.RepaintManager.access$1100(RepaintManager.java:62)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1677)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
最佳答案
您的第二个迭代器循环不正确。
Iterator<Enemy> downwardIterator = enemyList.iterator();
while (iterator.hasNext()) {
// ...
应该是
Iterator<Enemy> downwardIterator = enemyList.iterator();
while (downwardIterator.hasNext()) {
// ...
编辑
您可能更喜欢 for-each
loop (使用隐藏迭代器)就像
for (Enemy de : enemyList) {
// ...
关于java - 嵌套迭代器,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/27025275/