firebase - Cloud Firestore: How to set a field in document to null

Question

I use a collection of documents that I use to identify user groups. My intention is to only fill in the document id field with the user id without having other useless fields in the documents. But after doing some research, apparently, it's not possible to have empty documents.

So, my question is how to set a (dummy) field in a document to null, which is supposedly supported by Firestore according to the documentation. I'm working on this in both Android and Web, but I suppose code for any platform is OK.

Update: I have confirmed that simply putting null as the field in Web works just fine, however, when I try the equivalent in Android like this:

Map<String, Object> emptyData = new HashMap<>();
emptyData.put("nullField", null);

Android Studio warns me:

Passing 'null' argument to parameter annotated as @NotNull

Should I keep passing null or is there something else I should do?

Answer 1

Waitting for answers