Firebase firestore NullPointerException

Question

java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.Date com.google.firebase.Timestamp.toDate()' on a null object reference

question from:https://stackoverflow.com/questions/66058254/firebase-firestore-nullpointerexception

Answer 1

I found out that this error occurs in my case because I'm updating multiple fields at the same time:

Map<String, Object> updates = new HashMap<>();
 updates.put("timestamp", FieldValue.serverTimestamp());
 updates.put("modifiedBy", firebaseUser.getUid());

documentReference.update(updates);

Now if you are using a repository and a viewmodel, the repositroy emits a value as each field is updated and timestamp may not be the first to be updated. I solved the issue by checking whether timestamp is null.