弹出上下文菜单抛出NullPointerException

Question

我使用chart实现了动态JFreeChart；但是，每当我右键单击时，Popup菜单都会出现错误。如果与我的代码有关，则记录器不会显示给我，而且我也不知道如何解决它。

以下是日志指出的内容：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at sun.font.FontDesignMetrics$MetricsKey.init(FontDesignMetrics.java:217)
    at sun.font.FontDesignMetrics.getMetrics(FontDesignMetrics.java:286)
    at sun.swing.SwingUtilities2.getFontMetrics(SwingUtilities2.java:1113)
    at javax.swing.JComponent.getFontMetrics(JComponent.java:1626)
    at sun.swing.MenuItemLayoutHelper.reset(MenuItemLayoutHelper.java:126)
    at javax.swing.plaf.synth.SynthMenuItemLayoutHelper.<init>(SynthMenuItemLayoutHelper.java:119)
    at javax.swing.plaf.synth.SynthGraphicsUtils.paint(SynthGraphicsUtils.java:501)
    at javax.swing.plaf.synth.SynthMenuUI.paint(SynthMenuUI.java:280)
    at javax.swing.plaf.synth.SynthMenuUI.update(SynthMenuUI.java:245)
    at javax.swing.JComponent.paintComponent(JComponent.java:780)
    at javax.swing.JComponent.paint(JComponent.java:1056)
    at javax.swing.JComponent.paintChildren(JComponent.java:889)
    at javax.swing.JComponent.paint(JComponent.java:1065)
    at javax.swing.JComponent.paintToOffscreen(JComponent.java:5210)
    at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1579)
    at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1502)
    at javax.swing.RepaintManager.paint(RepaintManager.java:1272)
    at javax.swing.JComponent._paintImmediately(JComponent.java:5158)
    at javax.swing.JComponent.paintImmediately(JComponent.java:4969)
    at javax.swing.RepaintManager$4.run(RepaintManager.java:831)
    at javax.swing.RepaintManager$4.run(RepaintManager.java:814)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
    at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:814)
    at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:789)
    at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:738)
    at javax.swing.RepaintManager.access$1200(RepaintManager.java:64)
    at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1732)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
    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)

这显示裁剪的弹出菜单：

它应该是这样的：

有人知道解决方案或遇到相同的问题吗？