Java Swing --如何辨别哪些代码正在调用组件上的绘图？

Question

在我的代码中的某个地方调用了绘图，但是堆栈跟踪完全不知道是什么和在哪里。它也是间歇性的，所以我知道这是一个线程问题，如果我设置一个断点，那么代码永远不会失败。那么，我该如何判断事件线程被调用的位置和方式来重绘组件呢？

下面是堆栈跟踪：

Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 4
    at javax.swing.plaf.basic.BasicTabbedPaneUI.paintTabArea(BasicTabbedPaneUI.java:834)
    at javax.swing.plaf.basic.BasicTabbedPaneUI.paint(BasicTabbedPaneUI.java:797)
    at javax.swing.plaf.ComponentUI.update(ComponentUI.java:161)
    at javax.swing.JComponent.paintComponent(JComponent.java:778)
    at javax.swing.JComponent.paint(JComponent.java:1054)
    at javax.swing.JComponent.paintChildren(JComponent.java:887)
    at javax.swing.JComponent.paint(JComponent.java:1063)
    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)

Answer 1

您可能正在EDT之外的GUI上执行操作。在您怀疑的每一段代码中，您可能想要使用SwingUtilities.isEventDispatchThread()来测试您当前是否处于EDT中。如果此方法返回false，则不应执行任何UI操作。

下面是一个如何使用它进行调试的示例：

public static void checkInEventDispatchThread(String pMethod) {
    if (!SwingUtilities.isEventDispatchThread()) {
        System.err.println("** NOT in EDT: " + pMethod + "() in " + 
                           Thread.currentThread().getName());
    }
}

对于你怀疑的每一段代码：

public void myMethod() {
    UtilClass.checkInEventDispatchThread("myMethod");
}

当然，这只是为了调试的目的，你不应该为了生产/发布而保留这样的调用。