How to get value of last node added to the database

I'm trying to access a certain value within the last added Firebase node. In my database I have a set of Clients, which through my app, can be added to. Inside a client there's a piece of information titled 'clientName'. I would like to get this value.

Once I get the value, I'm trying to give a toast message showing that value.

Here is my code inside the onClick method of my button. I'm not sure why it's not working. If you know of another way I could do this or a way to fix my current code I'd really appreciate it!

Thanks in advance guys!

my_button[bt].setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            if (my_button[Index].getId() == ((ImageButton) v).getId()) {
                                String bla = (String) getIntent().getExtras().get("id");
                                String address = "https://console.firebase.google.com/project/cssecond-92a2d/database/data/clients/" +bla+"/clientName";
                                Firebase ref = new Firebase(address);
                                ref.addListenerForSingleValueEvent(new ValueEventListener() {
                                    @Override
                                    public void onDataChange(com.firebase.client.DataSnapshot dataSnapshot) {
                                        String value = (String) dataSnapshot.getValue();
                                        Toast.makeText(HomePageNews.this,"In your hands you have: "+ value ,Toast.LENGTH_LONG).show();

                                    }

                                    @Override
                                    public void onCancelled(FirebaseError firebaseError) {

                                    }
                                });

                            }
                        }
                    });