CODEWITHSUNDEEP
androidfirebasefirebase-realtime-databasetimestamp
Erik
Erik

Reputation: 5119

How does Firebase ServerValue.TIMESTAMP work in this situation

I read in this answer about ServerValue.TIMESTAMP that the ValueEventListener will fire twice with first the local time and then with server time.. My question is will that only happen if the code look like this using setValue:

ref.addValueEventListener(new ValueEventListener() {
    public void onDataChange(DataSnapshot dataSnapshot) {
        System.out.println(dataSnapshot.getValue()); 
    }

    public void onCancelled(DatabaseError databaseError) { }
});
ref.setValue(ServerValue.TIMESTAMP);

Or will it also happen if the call is a updateChildren like this, notice the ServerValue.TIMESTAMP

Map<String, Object> someMap = new HashMap<>();
someMap.put("id", 239231);
someMap.put("time", ServerValue.TIMESTAMP);
someMap.put("name", "some name");
Map<String, Object> childUpdates = new HashMap<>();
childUpdates.put("someKey", someMap);
mFirebase.updateChildren(childUpdates, new CompletionListener() {
    @Override
    public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) {

    }
});

UPDATE

Here´s what I try to do.
In the Firebase code lab for Friendly Chat app(friendlychat). I replace the send chat message code that look like this:

FriendlyMessage friendlyMessage = new 
               FriendlyMessage(mMessageEditText.getText().toString(),
                               mUsername,
                               mPhotoUrl,
                               null /* no image */);
       mFirebaseDatabaseReference.child(MESSAGES_CHILD)
               .push().setValue(friendlyMessage);

with an childUpdates instead like this:

        final String pushKeyAddress = mFirebaseDatabaseReference.child(MESSAGES_CHILD).push().getKey();
                Map<String, Object> someMap = new HashMap<>();
                someMap.put("text", mMessageEditText.getText().toString());
                someMap.put("name", mUsername);
                someMap.put("photoUrl", mPhotoUrl);
                someMap.put("time", ServerValue.TIMESTAMP);
                Map<String, Object> childUpdates = new HashMap<>();
                childUpdates.put(MESSAGES_CHILD.concat("/").concat(pushKeyAddress), someMap);
                mFirebaseDatabaseReference.updateChildren(childUpdates, new DatabaseReference.CompletionListener() {
                    @Override
                    public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) {
                        System.out.println(databaseError);
                    }

                });

And I see the CompletionListener onComplete only fires once and not twice as I would expect since I use the ServerValue.TIMESTAMP

Upvotes: 0

Views: 531

Answers (1)

Frank van Puffelen
Frank van Puffelen

Reputation: 598797

My answer (which you link in the question) explains what happens in "in a write operation". The same thing will happen for either a setValue() and an updateChildren().

Upvotes: 1

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