title: Firebase error: Can´t add ValueEventListener
body: <p>Here is my declaration code:</p>
  
  <pre><code>database = FirebaseDatabase.getInstance();
  myRef = database.getReference("lifts");
  </code></pre>
  
  <p>Why can't I add the <code>ValueEventListener</code>? I tried the sample from the Firebase Guide. Here is the code:</p>
  
  <pre><code>myRef.addValueEventListener(new ValueEventListener() {
      @Override
      public void onDataChange(DataSnapshot dataSnapshot) {
  
      }
  
      @Override
      public void onCancelled(FirebaseError firebaseError) {
  
      }
  });
  </code></pre>
  
  <p>This works and I have no idea why?</p>
  
  <pre><code>myRef.addValueEventListener(new com.google.firebase.database.ValueEventListener() {
      @Override
      public void onDataChange(com.google.firebase.database.DataSnapshot dataSnapshot) {
          for (com.google.firebase.database.DataSnapshot item: dataSnapshot.getChildren()) {
              ...
          }
          ...
      }
  });    
  </code></pre>