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 =  MyclientFacade.getUser();
If (myUser.getScore > 10) {
    DoSomething() 
}

Where User is a POJO filled by Firebase;

The problem occurs when the Firebase cache is activated

Firebase.getDefaultConfig().setPersistenceEnabled(true);

and the user is already in cache and the data are updated on Firebase DB by a third party (or even by another device). Indeed when I query Firebase to get the User I obtain first the data from the cache and later a second change event with the latest data from the Firebase server, but it's too late!

Let's see the synchronous method MyclientFacade.getUser() :

Public User  getUser()  {
  Firebase ref = myFireBaseroot.child("User").child(uid);
  ref.keepSynced(true);
  /* try {
    Thread.sleep(3000);
 } catch (InterruptedException e) {
    e.printStackTrace();
 }*/
final CountDownLatch signal = new CountDownLatch(1);

ref.addListenerForSingleValueEvent(new ValueEventListener() {
//ref.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
       this.user = dataSnapshot.getValue(User.class);
       signal.countDown();
    }
    @Override
    public void onCancelled(FirebaseError firebaseError) {
       signal.countDown();
    }
});
signal.await(5, TimeUnit.SECONDS);
ref.keepSynced(false);
return this.user;
}

I obtain the same behavior if I use addValueEventListener or addListenerForSingleValueEvent mixed with ref.keepSynced:

Let's say my user's score value in cache is 5 and from Firebase DB is 11.

When I call getUser I will obtain the score of 5 (Firebase ask cache first) so I will not call the doSomething() method.

If I uncomment the Thread.sleep() code from my example, the Firebase cache will have enough time to be updated and my getUser will return the correct score value (11).

So how can I directly ask the latest value directly from server side and bypass the cache?

Answer 1

Waitting for answers