How to get data from Real-Time Database in Firebas

Question

I've used the Real-Time Database with this setup:

->users
    ->uid
        ->name
        ->email
        ->other info

If I wanted to save the user data I would use my User class and then set the object in the database like this:

//assume variables have already been declared...

mFirebaseAuth = FirebaseAuth.getInstance();
mFirebaseUser = mFirebaseAuth.getCurrentUser();
User user = new User(name, email, other values...);
mDBRef.child("users").child(mFirebaseUser.getUid()).setValue(user);

I tried it and it works fine.

But how can I retrieve these values from the database? For instance, once I set a User object as shown above, I may want to retrieve the user's email. I don't mean getting the email through the sign-in provider. I want the email through the real-time database. I've tried working this out for a while now but the documentation isn't helping much. All it shows is to setup listeners in order to wait for changes to the data. But I'm not waiting for changes, I don't want a listener. I want to directly get the values in the database by using the keys in the JSON tree. Is this possible via the real-time database? If so, how can it be done because either the documentation doesn't explain it or I'm just not understanding it. If not possible, am I supposed to be using the Storage database or something else? Thanks.

Answer 1

Firebase uses listeners to get data. That is just the nature of how it works. Although, you can use a single event listener (the equivalent of just grabbing the data once). It will fire immediately and get the data, and will not fire ever again. Here's a code example to get the current user's email:

//Get User ID
final String userId = getUid();

//Single event listener
mDatabase.child("users").child(userId).addListenerForSingleValueEvent(
    new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            // Get user value
            User user = dataSnapshot.getValue(User.class);

            //user.email now has your email value
        }
    });