Question

我正在编写一个简单的Snake游戏。所以，我有一个更新线程，执行一个无限的while循环，它会更新所有GameObject并重新绘制JPanel。

// Run thread
public void run () {
    try {
        while (true) {
            this.update();
            this.getGamePanel().sceneShouldRepaint();

            Thread.sleep(this.getFps());
        }
    }
    catch (Exception e) {
        JOptionPane.showMessageDialog(null, e.getMessage(), "Error", JOptionPane.OK_CANCEL_OPTION);
    }
}

现在，问题在于，当我调用myJFrame.repaint()时，它可能正在另一个线程中执行。当我画画时，我显然必须得到物体的位置，速度等等...... 我知道异常来自paintComponent()，因为它没有被捕获。如您所见，while循环嵌入在try-catch中。

我该怎么办？

这是例外：

Exception in thread "AWT-EventQueue-0" java.util.ConcurrentModificationException
    at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
    at java.util.AbstractList$Itr.next(AbstractList.java:343)
    at ch.ilijatovilo.Scene.GameObjects.Creatures.Snake.Snake.render(Snake.java:52)
    at ch.ilijatovilo.Scene.SceneHandling.Scene.renderSceneObjects(Scene.java:57)
    at ch.ilijatovilo.Scene.SceneHandling.Scene.render(Scene.java:53)
    at ch.ilijatovilo.Scene.SceneHandling.GamePanel.paintComponent(GamePanel.java:53)
    at ch.ilijatovilo.Scene.SceneHandling.GamePanel.paint(GamePanel.java:30)
    at javax.swing.JComponent._paintImmediately(JComponent.java:5106)
    at javax.swing.JComponent.paintImmediately(JComponent.java:4890)
    at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:812)
    at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:714)
    at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:694)
    at javax.swing.RepaintManager.access$700(RepaintManager.java:41)
    at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1672)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:702)
    at java.awt.EventQueue.access$400(EventQueue.java:82)
    at java.awt.EventQueue$2.run(EventQueue.java:663)
    at java.awt.EventQueue$2.run(EventQueue.java:661)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:672)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

感谢您的帮助！

HINT

如果您尝试从2个不同的线程同时访问实例，则抛出ConcurrentModificationException。这至少是我听说过的。

更多代码

// This is the render method in the Snake class at line 50.
// So 52 is the start of the for loop

public void render(Graphics g) {
    // We delegate the drawing to the body parts
    for (SnakeBodyPart sbp : this.getSnakeBodyParts()) {
        sbp.render(g);
    }

    this.getSnakeHead().render(g);
}

// And here the for loop from the Scene class
protected void renderSceneObjects (Graphics g) {
    for (SceneObject so : this.getSceneObjects()) {
        so.render(g);
    }
}

Answer 1

很可能你正在改变需要在另一个线程中呈现的细节，这个库看起来不允许（我认为大多数GUI库都不允许这样做）

当您更改GUI组件或将要呈现的内容时，您需要调用SwingUtils.invokeLater()，以便任务将在GUI事件线程中执行，而不是在另一个线程中同时执行。

Answer 2

CopyOnWriteArrayList是一个答案。当我有时间的时候，我会照顾另一种解决方案......

基于awt的应用程序中的另一个解决方案应该是

EventQueue.invokeLater(new Runnable() {...});

Answer 3

如果你在两个线程中调整列表，你会看到像你提到的问题。如果您无法找到'Comodification'，您可以依靠java.util.concurrent库。

http://docs.oracle.com/javase/tutorial/essential/concurrency/collections.html

简单游戏中的ConcurrentModificationException

3 个答案: