【转】JTree调用UpdateUI()抛空指针

最近在做东西时发现，当在线程里面刷新JTree时，有时会出现空指针错误，在网上查了很久，终于发现以下解决方法：

JTree中调用UpdateUI()报以下错误

java.lang.NullPointerException
at javax.swing.plaf.basic.BasicTreeUI.paintRow(BasicTreeUI.java:1367)
at javax.swing.plaf.basic.BasicTreeUI.paint(BasicTreeUI.java:1171)
at javax.swing.plaf.metal.MetalTreeUI.paint(MetalTreeUI.java:152)
at javax.swing.plaf.ComponentUI.update(ComponentUI.java:142)
at javax.swing.JComponent.paintComponent(JComponent.java:541)
at javax.swing.JComponent.paint(JComponent.java:808)
at javax.swing.JComponent.paintWithOffscreenBuffer(JComponent.java:4787)
at javax.swing.JComponent.paintDoubleBuffered(JComponent.java:4740)
at javax.swing.JComponent._paintImmediately(JComponent.java:4685)
at javax.swing.JComponent.paintImmediately(JComponent.java:4488)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:410)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:117)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:454)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)

>>>>>>
必须在事件处理线程中操作Swing组件，如果像你的程序中那样需要在别的线程中操作Swing组件的话，要使用下面这样的方法：

SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
tree.updateUI();
}
});

本文转自：http://raymanan.iteye.com/blog/580337