title: Firebase Realtime Database addChildEventListener fetch all items when app reopen
body: <p><code>addValueEventListener</code> gives all the data whenever something changed in the database, due to this I have implemented <code>addChildEventListener</code> to get the only new item when there is a something new in the database.</p>
  
  <p>Currently, the problem I am facing is whenever I open app, <code>addChildEventListener</code> fetch all the item one by one in <code>onChildAdded</code> method.</p>
  
  <p>Is there any way that I can fetch only new items in Firebase Realtime Database? Here is my code:</p>
  
  <pre><code>                mDatabase.addChildEventListener(new ChildEventListener() {
                  @Override
                  public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                      News news = dataSnapshot.getValue(News.class);
                      Log.i("YES-onChildAdded", news.getId()+"/"+news.getHeadline());
                  }
  
                  @Override
                  public void onChildChanged(DataSnapshot dataSnapshot, String s) {
                      News news = dataSnapshot.getValue(News.class);
                      Log.i("YES-onChildChanged", news.getId()+"/"+news.getHeadline());
                  }
  
                  @Override
                  public void onChildRemoved(DataSnapshot dataSnapshot) {
                      News news = dataSnapshot.getValue(News.class);
                      Log.i("YES-onChildRemoved", news.getId()+"/"+news.getHeadline());
                  }
  
                  @Override
                  public void onChildMoved(DataSnapshot dataSnapshot, String s) {
                      News news = dataSnapshot.getValue(News.class);
                      Log.i("YES-onChildMoved", news.getId()+"/"+news.getHeadline());
                  }
  
                  @Override
                  public void onCancelled(DatabaseError databaseError) {
                      Log.i("YES-Cancelled", databaseError.getMessage());
                  }
              });
  </code></pre>