ComboBoxes Behaving Inconsistently in JFlowRibbonBands

[MichaelWDenney]

I feel I must have just have missed something simple. I have three comboboxes in JFlowRibbonBands. When you click on two of them, the dropdown appears and you have the option of using the up/down arrow keys to move through the selections. In the third, clicking on it makes the dropdown appear, but if you attempt to use the up/down arrows it immediately takes the next selection, closes the dropdown and gives the following exception:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "javax.swing.JComboBox.repaint()" because "this.comboBox" is null
at java.desktop/javax.swing.plaf.basic.BasicComboBoxUI.selectPreviousPossibleValue(BasicComboBoxUI.java:1235)
at java.desktop/javax.swing.plaf.basic.BasicComboBoxUI$Actions.actionPerformed(BasicComboBoxUI.java:1659)
at java.desktop/javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1810)
at java.desktop/javax.swing.JComponent.processKeyBinding(JComponent.java:2956)
at java.desktop/javax.swing.JComboBox.processKeyBinding(JComboBox.java:1461)
at java.desktop/javax.swing.JComponent.processKeyBindings(JComponent.java:3018)
at java.desktop/javax.swing.JComponent.processKeyEvent(JComponent.java:2918)
at java.desktop/javax.swing.JComboBox.processKeyEvent(JComboBox.java:1453)

Note that, besides the exception, the combobox works fine. Even the arrow key support isn't exactly a problem. It is just not consistent with the other two. Any ideas?

[MichaelWDenney]

Actually I may need to take back my last statement. The combobox in which the up/down arrows does not always work as expected. It occasionally does not trigger its event. When this occurs, making a new selection gets things working again, but attempting to re-select the failed selection has no effect, presumably because a change is not being recognized by the combobox logic.

[kirill-grouchnikov]

Ribbon comboboxes (JRibbonComboBox) are thin wrappers around the core Swing comboboxes, along with tracking selection changes and notifying the selection listener set on the content model.

Without a simple sample that shows this problem, I would say to check what is the custom selection logic you have in your model, if it's doing some complex logic that might be offloading something to a worker thread. And try to reproduce this with a standalone combobox without the JRibbonComboBox extra selection handling.