ImmutableEmpty or some other more specific default selection is probably the "best" way to go, but null is used in comboboxes often enough to mean nothing selected. Either as a default, or because the user really might want to choose nothing. Maybe not handling null will force people to do it the other way 🤷

But sometimes you don't have a better way. Lets say you are showing an enum from a library you have no control over. But "none" isn't in the enum, but should be an option in the gui? I guess the next best thing would be to create a wrapper class around the enum that you can then have a "NotSelected" instance of.

Don't forget, this discussion just applies to ComboBox. ChoiceBox works as Thomas wanted. You can add and select a true null value.

Swing JComboBox supports nulls, but there's no Combo/Choice split in Swing

what is the difference? i'm guessing choice doesn't allow user input?

I have to agree with @alex - null in a combobox is problematic, because it would be impossible for the combobox to determine which item is selected. Think about it - the list selection listener does lots of

indexOf()

calls, which would return -1 for

null

. @thomasnield Maybe you can create a custom subclass of your domain object that means

null

? If you have

Customer

, then add

class NullCustomer : Customer

?

FYI

null

selection was always allowed in ComboBox

Also, as @Spike Baylor alluded to - how would you set null then? 🙂

@abhinay Yes, absolutely. Selecting none of the values is totally fine, and that's part of the problem with wanting

null

to represent one of the items 🙂

AFAIR, you can have your backed list not contain

null

and still set the value of ComboBox to

null

Yes, absolutely 🙂

Not to speak for @thomasnield but i wonder if this is just a swing -> javafx issue. I wonder if ChoiceBox would just be the better solution, and because swing doesn't have one, we're used to making combobox work in ways it probably shouldn't.

as Carl alluded to

Ah, I didn't pay attention - was already mentioned 🙂

I just had to try - adding two or more null values to a choicebox. The first null value is always selected, even when you select any of the other null values.

@edvin i think people expect a null selection to clear the value. it's been in Swing for decades now. 8u20 is like 5 years ago

@carlw I think it would be cleaner if you enabled empty selection, and the default empty selection item could be null for example.

@edvin or maybe just have a button to clear() the value rather than have a null in the backing list

I'm going to try

ChoiceBox

right now. Never used it before

ChoiceBox

seems to work great for now. But @abhinay I'm glad to see the issue was fixed in JavaFX 9.

I think it will do what you want.

@edvin yeah an isRequired flag, but also a way to "select nothing" as a way to clear the selection

@thomasnield Hmm.. good idea.. Depending on the sematics / UI maybe an explicit action to set null would make more sense even. But if ChoiceBox works, we might have a workaround until Java 11 at least 🙂

@carlw Yes, absolutely

@edvin yeah if I was stuck with

ComboBox

I would have a tiny eraser button or something next to it. But for now, yes the

ChoiceBox

is a good workaround

Separate note, I am close to getting RxJavaFX for Java 11 out. @carlw or anybody who is savvy with artifacts, what would cause my POM file to be missing properties on Bintray? I'm a bit of a noob with more complicated artifiact deployments.

do you use gradle or maven to deploy to bintray?