Swing 事件调度期间发生异常：java.lang.NullPointerException:颜色不能为null

当我启动一个GUI应用程序时，下面的异常会出现很多次（大约8次）

导致异常的确切行是： GradientPaint titleGradient=GradientPaint（0,0，选择的标题颜色

请注意，selectedTitleColor变量已经在类中的其他地方设置了一个值：： public void installDefaults（）{

---

selectedTitleColor=UIManager.getColor（“InternalFrame.activeTitleBackground”）

编译器不会说谎。请尝试在调试模式下运行代码，并设置断点，以便您可以查看

selectedTitleColor

和

selectedTitleGradientColor

的值。我保证其中至少有一个将

为null

我同意您的看法，编译器不会说谎。问题的发生是由于ear使用

selectedTitleColor

，早期是指在另一种方法

selectedTitleColor=UIManager.getColor（“InternalFrame.activeTitleBackground”）；

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Colors cannot be null
at java.awt.GradientPaint.<init>(GradientPaint.java:71)
at it.soltec.ibox.client.components.IBFrameTitlePane.paintTitleBackground(IBFrameTitlePane.java:1065)
at it.soltec.ibox.client.components.IBFrameTitlePane.paintComponent(IBFrameTitlePane.java:1008)
at javax.swing.JComponent.paint(JComponent.java:1029)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JLayeredPane.paint(JLayeredPane.java:567)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JViewport.paint(JViewport.java:747)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at it.soltec.ibox.client.IBoxMainFrame$MyPanel.paint(IBoxMainFrame.java:6595)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JLayeredPane.paint(JLayeredPane.java:567)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5131)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1479)
at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1410)
at javax.swing.RepaintManager.paint(RepaintManager.java:1224)
at javax.swing.JComponent.paint(JComponent.java:1015)
at java.awt.GraphicsCallback$PaintCallback.run(GraphicsCallback.java:21)
at sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:60)
at sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:97)
at java.awt.Container.paint(Container.java:1780)
at java.awt.Window.paint(Window.java:3375)
at it.soltec.ibox.client.IBoxMainFrame.paint(IBoxMainFrame.java:6014)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:713)
at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:693)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:125)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:641)
at java.awt.EventQueue.access$000(EventQueue.java:84)
at java.awt.EventQueue$1.run(EventQueue.java:602)
at java.awt.EventQueue$1.run(EventQueue.java:600)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:611)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

    protected void paintTitleBackground(Graphics g) {
    if ( g instanceof Graphics2D) {
        Graphics2D g2 = (Graphics2D) g;
        Paint savePaint = g2.getPaint();
        boolean isSelected = frame.isSelected();
        int w = getWidth();

       // selectedTitleColor =  Color.WHITE;
       // selectedTitleGradientColor = Color.ORANGE;
        if (isSelected) {
            GradientPaint titleGradient =
                    new GradientPaint(0, 0, selectedTitleColor,
                                              (int) (w * .75), 0, selectedTitleGradientColor);