// Login button
    Button loginButton = (Button) findViewById(R.id.loginBtn);
    loginButton.setOnClickListener(new Button.OnClickListener()
    {
        public void onClick(View v)
        {
            loginTask.execute("");
        }
    });


// Background login thread
private AsyncTask<Object, String, String> loginTask = new AsyncTask<Object, String, String>(){

    @Override
    protected String doInBackground(Object... arg0)
    {
        Log.v(TAG, "Login task started");
        LoginManager lm = new LoginManager();
        String username = emailText.getText().toString();
        String password = passwordText.getText().toString();
        loginBundle = new Bundle();
        loginBundle.putString(Constants.LOGIN_HANDLER_ID, lm.login(username, password));
        loginMessage = Message.obtain(null, 0);
        loginMessage.setData(loginBundle);
        loginHandler.sendMessage(loginMessage);
        return "";
    }

};

new LoginTask().execute("");

private class LoginTask extends
    AsyncTask<Object,String, String> {
.....

}