@Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Firebase.setAndroidContext(this);
    mFirebaseRef = new Firebase("https://codelabg.firebaseio.com");

    final EditText textEdit = (EditText) this.findViewById(R.id.text_edit);
    Button sendButton = (Button) this.findViewById(R.id.send_button);

    sendButton.setOnClickListener(
        new View.OnClickListener() {
          @Override
          public void onClick(View v) {
            String text = textEdit.getText().toString();
            ChatMessage message = new ChatMessage(email, text);
            mFirebaseRef.push().setValue(message);
            textEdit.setText("");
          }
        });

    final ListView listView = (ListView) this.findViewById(android.R.id.list);
    mListAdapter =
        new FirebaseListAdapter<ChatMessage>(
            this, ChatMessage.class, android.R.layout.two_line_list_item, mFirebaseRef) {
          @Override
          protected void populateView(View v, ChatMessage model, int position) {
            ((TextView) v.findViewById(android.R.id.text1)).setText(model.getName());
            ((TextView) v.findViewById(android.R.id.text2)).setText(model.getText());
          }
        };
    listView.setAdapter(mListAdapter);

    // Step 5.6: gọi showFirebaseLoginPrompt() khi loginButton được click.
    // Truy cập https://codelabg.firebaseio.com -> chọn tab: Auth -> chọn Add User để thêm user.
    loginButton = (Button) this.findViewById(R.id.login);
    loginButton.setOnClickListener(
        new View.OnClickListener() {
          @Override
          public void onClick(View v) {
            showFirebaseLoginPrompt();
          }
        });

    logoutButton = (Button) this.findViewById(R.id.logout);
    logoutButton.setOnClickListener(
        new View.OnClickListener() {
          @Override
          public void onClick(View v) {
            logout();
          }
        });
  }
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    ref = getFirebaseRef();

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(
        new View.OnClickListener() {
          @Override
          public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                .setAction("Action", null)
                .show();
          }
        });
  }