We've created a component (JYTabbedPane) which dynamically adds sub-components when a related event occurs. In this case the sub component is a JYLabel which is used as tab title.

Unfortunately the event occurs while FormLAF temporary removed related keys from the UIDefaults which leads to the exception below.

UIDefaults.getUI() failed: no ComponentUI class for: de.javasoft.swing.plaf.basic.BasicJYTabbedPaneUI$5[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=,f
lags=0,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,horizontalAlignment=LEADING,horizontalTextPosition=TRAILING,iconTextGap=4,labelFor=,t
ext=,verticalAlignment=CENTER,verticalTextPosition=CENTER]
java.lang.Error
        at javax.swing.UIDefaults.getUIError(UIDefaults.java:712)
        at javax.swing.MultiUIDefaults.getUIError(MultiUIDefaults.java:133)
        at javax.swing.UIDefaults.getUI(UIDefaults.java:742)
        at javax.swing.UIManager.getUI(UIManager.java:989)
        at org.jdesktop.swingx.plaf.LookAndFeelAddons.getUI(LookAndFeelAddons.java:308)
        at de.javasoft.swing.JYLabel.updateUI(JYLabel.java:76)
        at javax.swing.JLabel.<init>(JLabel.java:145)
        at javax.swing.JLabel.<init>(JLabel.java:175)
        at de.javasoft.swing.JYLabel.<init>(JYLabel.java:51)
        at de.javasoft.swing.JYLabel.<init>(JYLabel.java:46)
        at de.javasoft.swing.plaf.basic.BasicJYTabbedPaneUI$5.<init>(BasicJYTabbedPaneUI.java:1039)
        at de.javasoft.swing.plaf.basic.BasicJYTabbedPaneUI.addTab(BasicJYTabbedPaneUI.java:1039)
        at de.javasoft.swing.plaf.basic.BasicJYTabbedPaneUI.access$17(BasicJYTabbedPaneUI.java:1031)
        at de.javasoft.swing.plaf.basic.BasicJYTabbedPaneUI$4.propertyChange(BasicJYTabbedPaneUI.java:819)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:339)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:276)
        at java.awt.Component.firePropertyChange(Component.java:8132)
        at de.javasoft.swing.JYTabbedPane.firePropertyChange(JYTabbedPane.java:1345)
        at de.javasoft.swing.JYTabbedPane.insertTab(JYTabbedPane.java:386)
        at org.netbeans.modules.form.layoutsupport.delegates.JTabbedPaneSupport.addComponentsToContainer(JTabbedPaneSupport.java:259)
        at org.netbeans.modules.form.layoutsupport.LayoutSupportManager.addComponentsToContainer(LayoutSupportManager.java:668)
        at org.netbeans.modules.form.VisualReplicator.addComponent(VisualReplicator.java:391)
        at org.netbeans.modules.form.VisualReplicator.updateAddedComponents(VisualReplicator.java:357)
        at org.netbeans.modules.form.FormDesigner$FormListener.run(FormDesigner.java:2452)
        at org.netbeans.modules.form.FormLAF$3.run(FormLAF.java:329)
        at org.openide.util.Mutex.doEventAccess(Mutex.java:1361)
        at org.openide.util.Mutex.readAccess(Mutex.java:271)
        at org.netbeans.modules.form.FormLAF.executeWithLookAndFeel(FormLAF.java:312)
        at org.netbeans.modules.form.FormDesigner$FormListener.processEvents(FormDesigner.java:2377)
        at org.netbeans.modules.form.FormDesigner$FormListener.formChanged(FormDesigner.java:2343)
        at org.netbeans.modules.form.FormModel.fireEvents(FormModel.java:1296)
        at org.netbeans.modules.form.FormModel.fireEventBatch(FormModel.java:1269)
        at org.netbeans.modules.form.FormModel.firePendingEvents(FormModel.java:1232)
        at org.netbeans.modules.form.FormModel.access$000(FormModel.java:68)
        at org.netbeans.modules.form.FormModel$2.run(FormModel.java:1212)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:148)
        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)

For some reason the issue does *not* occur when the component type (JYLabel) already exists in the form - before adding JYTabbedPane.

After some investigations what's going wrong, the issue seems to be caused by the FormLAF.useDesignerLookAndFeel(...) method which temporary removes keys from the UIDefaults. While the keys are removed our component tries to create sub-components and fails.

Related code line from FormLAF.useDesignerLookAndFeel:
  defaults.keySet().removeAll(netbeansDefaults.keySet());

The issue also occurs with NetBeans 6.9.

Thanks,
Wolfgang