Exception beim Öffnen einer JComboBox, die auf einem JPopupMenu sitzt

[Michael Schyroky]

Hallo,

<P>ich bekomme folgende Exception, wenn ich eine JComboBox öffnen möchte, die auf einem JPopupMenu sitzt:

<P>java.lang.NullPointerException
<BR>at javax.swing.plaf.basic.BasicPopupMenuUI$MouseGrabb er.grabContainer(BasicPopupMenuUI.java:383)
<BR>at javax.swing.plaf.basic.BasicPopupMenuUI$MouseGrabb er.requestAddGrab(BasicPopupMenuUI.java:267)
<BR>at javax.swing.plaf.basic.BasicPopupMenuUI$MouseGrabb er.stateChanged(BasicPopupMenuUI.java:323)
<BR>at javax.swing.MenuSelectionManager.fireStateChanged( MenuSelectionManager.java:161)
<BR>at javax.swing.MenuSelectionManager.setSelectedPath(M enuSelectionManager.java:87)
<BR>at javax.swing.JPopupMenu.setVisible(JPopupMenu.java: 751)
<BR>at javax.swing.JPopupMenu.show(JPopupMenu.java:927)
<BR>at javax.swing.plaf.basic.BasicComboPopup.show(BasicC omboPopup.java:177)
<BR>at javax.swing.plaf.basic.BasicComboPopup.togglePopup (BasicComboPopup.java:982)
<BR>at javax.swing.plaf.basic.BasicComboPopup$InvocationM ouseHandler.mousePressed(BasicComboPopup.java:632)
<BR>at java.awt.AWTEventMulticaster.mousePressed(AWTEvent Multicaster.java:222)
<BR>at java.awt.Component.processMouseEvent(Component.jav a:5097)
<BR>at java.awt.Component.processEvent(Component.java:489 7)
<BR>at java.awt.Container.processEvent(Container.java:156 9)
<BR>at java.awt.Component.dispatchEventImpl(Component.jav a:3615)
<BR>at java.awt.Container.dispatchEventImpl(Container.jav a:1627)
<BR>at java.awt.Component.dispatchEvent(Component.java:34 77)
<BR>at java.awt.LightweightDispatcher.retargetMouseEvent( Container.java:3483)
<BR>at java.awt.LightweightDispatcher.processMouseEvent(C ontainer.java:3195)
<BR>at java.awt.LightweightDispatcher.dispatchEvent(Conta iner.java:3128)
<BR>at java.awt.Container.dispatchEventImpl(Container.jav a:1613)
<BR>at java.awt.Window.dispatchEventImpl(Window.java:1606 )
<BR>at java.awt.Component.dispatchEvent(Component.java:34 77)
<BR>at java.awt.EventQueue.dispatchEvent(EventQueue.java: 456)
<BR>at java.awt.EventDispatchThread.pumpOneEventForHierar chy(EventDispatchThread.java:201)
<BR>at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:151)
<BR>at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:145)
<BR>at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:137)
<BR>at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:100)

<P>Was sagt mir diese Meldung, und wie kann ich doch noch mit einer JComboBox auf einem JPopupMenu arbeiten?

<P>Jetzt kann ich nur noch hoffe, dass ich nicht der einzige mit diesem Problem bin ;-)

Danke im voraus und Gruss
<BR> Michael