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

Answer 3

just fetch specific node data and its working perfect for me

mFirebaseInstance.getReference("yourNodeName").getRef().addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {


        for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
            Log.e(TAG, "======="+postSnapshot.child("email").getValue());
            Log.e(TAG, "======="+postSnapshot.child("name").getValue());
        }
    }

    @Override
    public void onCancelled(DatabaseError error) {
        // Failed to read value
        Log.e(TAG, "Failed to read app title value.", error.toException());
    }
});

Answer 4

I store my data this way:

accountsTable ->
  key1 -> account1
  key2 -> account2

in order to get object data:

accountsDb = mDatabase.child("accountsTable");

accountsDb.child("some   key").addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot snapshot) {

                    try{

                        Account account  = snapshot.getChildren().iterator().next()
                                  .getValue(Account.class);


                    } catch (Throwable e) {
                        MyLogger.error(this, "onCreate eror", e);
                    }
                }
                @Override public void onCancelled(DatabaseError error) { }
            });