Question

My client is complaining that JComboBox popups often close when the scroll is being used over a JComboBox popup with no vertical scrollbar. (He seems to accidently use scrolling over it because he is using an Apple Magic Mouse.)

Any way to prevent this to happen ?

I know it has to do with the ComboBoxUI, but I would like a few pointer where to start. BasicComboPopup.handler is private (not reusable) and I don’t see any code relative to any a MouseWhellListener in BasicComboPopup.

Answer 1

As seen in the source, BasicPopupMenuUI contains a nested class, MouseGrabber, that implements the AWTEventListener interface. The receipt of MouseEvent.MOUSE_WHEEL in eventDispatched() cancels the popup as a function of isInPopup(). I know of no simple way to defeat the behavior.

Empirically, this example invokes show() from the actionPerformed() handler of a JButton; mouse wheel events are ignored. This might be a reasonable alternative for your user, perhaps combined with a suitable ActionEvent modifier mask.

In contrast, this example invokes show() in response to isPopupTrigger() in a MouseAdapter; as expected, mouse wheel events cancel the popup.