Adding support for null values to Vaadin ComboBox
Vaadin 8 used to have the
ComboBox.setNullSelectionAllowed(true) function which enabled
the user to select an empty item in the ComboBox. Vaadin 14 does not seem to
have the same function, so what to do next?
At first, I tried to add the
null item amongst the list of items set via
combobox.setItems([null] + items)
But that only resulted in a NullPointerException with the message
"Cannot provide an id for a null item." thrown from
You could hack around, by overriding the
getId() method and making it return an empty string
in case of a null item, but once you start using lazy loading, you’ll quickly hit a dead end.
The solution is to show the “Clear” button as follows: