Android Firebase, simply get one child object's data

Question

I have been looking for a way to get one child object's data in Android Firebase.

I have found things like Firebase retrieve child Android. All the solutions are suggesting using a "ChildEventListener", however I need to get this data at this moment, not when it is moved, deleted, updated, etcetera.

My data is kept in https://.firebaseio.com/users//creation as a string. I figure there must be some simple way to access that without needing to do too much, because if I copy the exact URL to my browser, I can see the: 'creation: "2015/05/31 21:33:55"' right there in my "Firebase Forge Dashboard".

How can I access this without a listener?

Answer 1

Firebase listeners fire for both the initial data and any changes.

If you're looking to synchronize the data in a collection, use ChildEventListener. If you're looking to synchronize a single object, use ValueEventListener. Note that in both cases you're not "getting" the data. You're synchronizing it, which means that the callback may be invoked multiple times: for the initial data and whenever the data gets updated.

This is covered in Firebase's quickstart guide for Android. The relevant code and quote:

FirebaseRef.child("message").addValueEventListener(new ValueEventListener() {   @Override   public void onDataChange(DataSnapshot snapshot) {     System.out.println(snapshot.getValue());  //prints "Do you have data? You'll love Firebase."   }   @Override   public void onCancelled(DatabaseError databaseError) {           } }); 

In the example above, the value event will fire once for the initial state of the data, and then again every time the value of that data changes.

Please spend a few moments to go through that quick start. It shouldn't take more than 15 minutes and it will save you from a lot of head scratching and questions. The Firebase Android Guide is probably a good next destination, for this question specifically: https://firebase.google.com/docs/database/android/read-and-write

Answer 2

You don't directly read a value. You can set it with .setValue(), but there is no .getValue() on the reference object.

You have to use a listener. If you just want to read the value once, you use ref.addListenerForSingleValueEvent().

Example:

Firebase ref = new Firebase("YOUR-URL-HERE/PATH/TO/YOUR/STUFF"); ref.addListenerForSingleValueEvent(new ValueEventListener() {    @Override    public void onDataChange(DataSnapshot dataSnapshot) {        String value = (String) dataSnapshot.getValue();         // do your stuff here with value     }     @Override    public void onCancelled(FirebaseError firebaseError) {     } }); 

Source: https://www.firebase.com/docs/android/guide/retrieving-data.html#section-reading-once