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我用Java开发了一个应用程序..

出现的问题是，第一次单击后，如果用户再次单击菜单，则会发生以下异常..

由于它显示来源未知，我无法调试它......

谁能帮我这个 ？？


Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at sun.font.FontDesignMetrics$MetricsKey.init(Unknown Source)
        at sun.font.FontDesignMetrics.getMetrics(Unknown Source)
        at sun.swing.SwingUtilities2.getFontMetrics(Unknown Source)
        at javax.swing.JComponent.getFontMetrics(Unknown Source)
        at sun.swing.SwingUtilities2.getFontMetrics(Unknown Source)
        at javax.swing.plaf.synth.SynthMenuItemUI.paint(Unknown Source)
        at javax.swing.plaf.synth.SynthMenuUI.paint(Unknown Source)
        at javax.swing.plaf.synth.SynthMenuUI.update(Unknown Source)
        at javax.swing.JComponent.paintComponent(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JComponent.paintChildren(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JComponent.paintChildren(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JLayeredPane.paint(Unknown Source)
        at javax.swing.JComponent.paintChildren(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JComponent.paintToOffscreen(Unknown Source)
        at javax.swing.BufferStrategyPaintManager.paint(Unknown Source)
        at javax.swing.RepaintManager.paint(Unknown Source)
        at javax.swing.JComponent._paintImmediately(Unknown Source)
        at javax.swing.JComponent.paintImmediately(Unknown Source)
        at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
        at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
        at javax.swing.RepaintManager.seqPaintDirtyRegions(Unknown Source)
        at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(Unknown Source)
        at java.awt.event.InvocationEvent.dispatch(Unknown Source)
        at java.awt.EventQueue.dispatchEvent(Unknown Source)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.run(Unknown Source)
4

2 回答 2

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 at sun.font.FontDesignMetrics$MetricsKey.init(Unknown Source)

检查字体的实例化。你需要在new Font(name, ...)某个地方使用。

于 2011-03-12T08:41:37.560 回答
0

我假设第一次单击是显示菜单和菜单项的单击。如果用户然后单击一个菜单项，并且您遇到异常，我敢打赌您还没有完全实例化与该菜单关联的某些菜单项组件。

希望这可以帮助。

约翰·多纳

于 2011-03-12T04:03:41.233 回答