Cloud Firestore: retrieving cached data via direct get?

Question

Retrieving data from the server may take some seconds. Is there any way to retrieve cached data in the meantime, using a direct get?

The onComplete seem

Answer 1

I just ran a few tests in an Android app to see how this works.

The code you need is the same, no matter if you're getting data from the cache or from the network:

    db.collection("translations").document("rPpciqsXjAzjpComjd5j").get().addOnCompleteListener(new OnCompleteListener() {
        @Override
        public void onComplete(@NonNull Task task) {
            DocumentSnapshot snapshot = task.getResult();
            System.out.println("isFromCache: "+snapshot.getMetadata().isFromCache());
        }
    });

When I'm online this prints:

isFromCache: false

When I go offline, it prints:

isFromCache: true

There is no way to force retrieval from the cache while you're connected to the server.

If instead I use a listener:

    db.collection("translations").document("rPpciqsXjAzjpComjd5j").addSnapshotListener(new DocumentListenOptions().includeMetadataChanges(), new EventListener() {
            @Override
            public void onEvent(DocumentSnapshot snapshot, FirebaseFirestoreException e) {
                System.out.println("listen.isFromCache: "+snapshot.getMetadata().isFromCache());
            }
        }
    );

I get two prints when I'm online:

isFromCache: true

isFromCache: false