Java 小程序 AWT-EventQueue-1 ArrayIndexOutOfBoundsException

Question

我创建了一个名为 lines 的 Vector，用于存储绘制线端点的坐标点。它通过从存储的坐标绘制线条来完成我想要的任务，但会产生以下异常：

Exception in thread "AWT-EventQueue-1" java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 10
    at java.util.Vector.get(Vector.java:748)
    at DrawPad.paint(DrawPad.java:149)
    at java.awt.Container.update(Container.java:1995)
    at sun.awt.RepaintArea.updateComponent(RepaintArea.java:255)
    at sun.awt.RepaintArea.paint(RepaintArea.java:232)
    at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:358)
    at java.awt.Component.dispatchEventImpl(Component.java:4967)
    at java.awt.Container.dispatchEventImpl(Container.java:2294)
    at java.awt.Component.dispatchEvent(Component.java:4713)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access0(EventQueue.java:97)
    at java.awt.EventQueue.run(EventQueue.java:709)
    at java.awt.EventQueue.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.awt.EventQueue.run(EventQueue.java:731)
    at java.awt.EventQueue.run(EventQueue.java:729)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

Answer 1

您的问题最有可能在这里：

for(int i = 0; i < lines.capacity(); i += 4)
            g.drawLine(lines.get(i), lines.get(i + 1), lines.get(i + 2), lines.get(i + 3));

您在 for 循环的每次迭代中将 i 递增 4。这意味着您正在访问 Vector 行的 0、1、2 和 3 元素的第一个循环。下一个循环您将访问 4、5、6、7。接下来您将访问 8、9、10、11。Vector 行中可能没有那么多元素。

Answer 2

您需要在调用 lines.get(i) 之前检查该元素是否存在。另外，使用 lines.size() 而不是 lines.capacity()。

for(int i = 0; i < lines.size(); i += 4)
{
    if((i+3) < lines.size())
    {
        g.drawLine(lines.get(i), lines.get(i + 1), lines.get(i + 2), lines.get(i + 3));
    }
}

Java 小程序 AWT-EventQueue-1 ArrayIndexOutOfBoundsException

Java Applet AWT-EventQueue-1 ArrayIndexOutOfBoundsException

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