title: Retrieving multiple data from firebase returning null
body: <p>I'm using a Firebase database to store and read a list of "clubs" in an Android app.
  Below there's the Json representation of that.</p>
  
  <pre><code>{
    "clubs" : [ {
      "id" : 1,
      "image" : {
        "allocationByteCount" : 589824,
        "byteCount" : 589824,
        "config" : "ARGB_8888",
        "density" : 320,
        "generationId" : 212,
        "height" : 384,
        "mutable" : false,
        "premultiplied" : true,
        "recycled" : false,
        "rowBytes" : 1536,
        "width" : 384
      },
      "name" : "Axis"
    }, {
      "id" : 2,
      "image" : {
        "allocationByteCount" : 589824,
        "byteCount" : 589824,
        "config" : "ARGB_8888",
        "density" : 320,
        "generationId" : 214,
        "height" : 384,
        "mutable" : false,
        "premultiplied" : true,
        "recycled" : false,
        "rowBytes" : 1536,
        "width" : 384
      },
      "name" : "Allies"
    }, {
      "id" : 3,
      "image" : {
        "allocationByteCount" : 589824,
        "byteCount" : 589824,
        "config" : "ARGB_8888",
        "density" : 320,
        "generationId" : 216,
        "height" : 384,
        "mutable" : false,
        "premultiplied" : true,
        "recycled" : false,
        "rowBytes" : 1536,
        "width" : 384
      },
      "name" : "Neutrals"
    } ]
  }
  </code></pre>
  
  <p>I'm using a FirebaseAdapter class to call methods upon the Firebase database.
  But it returns null when trying to get all clubs.</p>
  
  <p>Bellow theres the method that calls it:</p>
  
  <pre><code>public List&lt;BDClub&gt; getClubs() {
  
          list.clear();
  
          database.getReference("clubs").addListenerForSingleValueEvent(new ValueEventListener() {
              @Override
              public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                  if (dataSnapshot.exists()){
                      System.out.println(dataSnapshot.getChildrenCount());
                      for(DataSnapshot array : dataSnapshot.getChildren()){
                          clubs = array.getValue(BDClub[].class);
                          for(BDClub c : clubs){
                              list.add(c);
                          }
                      }
                  }
              }
  
              @Override
              public void onCancelled(@NonNull DatabaseError databaseError) {
  
              }
  
          });
  
          return list;
      }
  </code></pre>
  
  <p>Is there a way to retrieve a list of clubs?
  Thanks in advance.</p>