Set parse username as action bar title

public class MessagingActivity extends Activity implements ServiceConnection, MessageClientListener {

    private Button sendButton;
    private EditText messageBodyField;
    private String messageBody;
    private MessageService.MessageServiceInterface messageService;
    private ParseUser mCurrentUser;
    private ServiceConnection serviceConnection = new MyServiceConnection();



    protected List<ParseUser> mUsers;
    protected ParseRelation<ParseUser> mContactsRelation;



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

        // Get the name from the exttra of the intent or howsoever you are getting the name

        doBind();
        bindService(new Intent(this, MessageService.class), serviceConnection, BIND_AUTO_CREATE);

        // setting the layout for text input
        messageBodyField = (EditText) findViewById(R.id.messageBodyField);


        //listen for a click on the send button
        sendButton = (Button) findViewById(R.id.sendButton);
        sendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                sendMessage();
            }
        });
    }

    private void sendMessage() {

        messageBodyField = (EditText) findViewById(R.id.messageBodyField);
        messageBody = messageBodyField.getText().toString();

        if (messageBody.isEmpty()) {
            Toast.makeText(this, "Please enter a message", Toast.LENGTH_LONG).show();
            return;
        }

        //Here is where you will actually send the message through to Sinch
        Toast.makeText(this, "Sending message! User id: " + mCurrentUser +  " Message: " + messageBody,
                Toast.LENGTH_LONG).show();
        messageBodyField.setText("");
    }


    @Override
    public void onResume() {
        super.onResume();

        mCurrentUser = ParseUser.getCurrentUser();
        mContactsRelation = mCurrentUser.getRelation(ParseConstants.KEY_CONTACTS_RELATION);

        setProgressBarIndeterminateVisibility(true);

        ParseQuery<ParseUser> query = ParseUser.getQuery();
        query.orderByAscending(ParseConstants.KEY_USERNAME);
        query.findInBackground(new FindCallback<ParseUser>() {

            @Override
            public void done(List<ParseUser> users, ParseException e) {
                setProgressBarIndeterminateVisibility(false);

                if (e == null) {
                    mUsers = users;

                    String[] usernames = new String[mUsers.size()];
                    int i = 0;
                    for(ParseUser user : mUsers){
                        usernames[i] = user.getUsername();
                        i++;


                    }

                    ActionBar actionbar = getActionBar();
                    actionbar.setTitle();



                }


            }

        });
    }