JTabbedPane NullPointerException

我使用netbeans visual creator在JFrame中創建了一個JTabbedPane。並建立一個JPanel。當我將JPanel添加爲選項卡時，出現以下錯誤。有時它不會發生。JTabbedPane NullPointerException

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException 
    at com.sun.java.swing.plaf.windows.WindowsTabbedPaneUI.paintContentBorder(WindowsTabbedPaneUI.java:145) 
    at javax.swing.plaf.basic.BasicTabbedPaneUI.paint(BasicTabbedPaneUI.java:791) 
    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:312) 
    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)

這是將JPanel作爲選項卡添加的代碼。

jTabbedPane2.addTab("Swimmer",new SwimmerPanel());

什麼是錯誤？

來源

2015-10-05 chamathabeysinghe

它看起來像jTabbedPane2仍然是空嘗試初始化並檢查 – soorapadman

眼下，這個問題應該被關閉（一個爲重複，兩個用於沒有可運行代碼）。考慮提供一個[可運行的示例]（https://stackoverflow.com/help/mcve），它可以證明你的問題。這不是代碼轉儲，而是您正在做的事情的一個例子，它突出了您遇到的問題。這將導致更少的混淆和更好的響應 – MadProgrammer

請參見[什麼是堆棧跟蹤，以及如何使用它來調試我的應用程序錯誤？]（http://stackoverflow.com/q/3988788/418556）＆[什麼是一個空指針異常，以及如何解決它？]（http://stackoverflow.com/q/218384/418556） –

你可能沒有初始化JTabbedPane的：

JTabbedPane jTabbedPane2 = new JTabbedPane();

來源

2015-10-06 08:00:14 sh5164

JTabbedPane NullPointerException

回答

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