How to bypass the Firebase cache to refresh data (in Android app)?

Question

On an Android application which must works offline most of the time I need, when it\'s online, to do some synchronous operations for i.e. :

User myUser =  My         


        

Answer 1

This was a problem that was causing me a lot of stress in my application too.

I tried everything, from changing .addListenerForSingleValueEvent() to .addValueEventListener() to trying to creatively use .keepSynced() to using a delay (the Thread.sleep() method you have described above) and nothing really worked consistently (even the Thread.sleep() method, which wasn't really acceptable in a production app didn't give me consistent results).

So what I did was this: after creating a Query object and calling .keepSynced() on it, I then proceed to write a mock/token object in the node I'm querying and THEN in that operation's completion listener, I do the data retrieval I want to do, after deleting the mock object.

Something like:

 MockObject mock = new MockObject();
    mock.setIdentifier("delete!");

    final Query query = firebase.child("node1").child("node2");

    query.keepSynced(true);

    firebase.child("node1").child("node2").child("refreshMock")
            .setValue(mock, new CompletionListener() {

                @Override
                public void onComplete(FirebaseError error, Firebase afb) {

                    query.addListenerForSingleValueEvent(new ValueEventListener() {

                        public void onDataChange(DataSnapshot data) {

                            // get identifier and recognise that this data
                            // shouldn't be used
                            // it's also probably a good idea to remove the
                            // mock object
                            // using the removeValue() method in its
                            // speficic node so
                            // that the database won't be saddled with a new
                            // one in every
                            // read operation

                        }

                        public void onCancelled(FirebaseError error) {
                        }

                    });

                }

            });
}

This has worked consistently so far for me! (well, for a day or so, so take this with a grain of salt). It seems like doing a write operation before reading somehow bypasses the cache, which makes sense. So the data comes back fresh.

The only downside is the extra write operation before the read operation, which may cause a small delay (obviously use a small object) but if that's the price for always fresh data, I'll take it!

Hope this helps!