public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {

        private final String mUsername;
        private final String mPassword;

        UserLoginTask(String username, String password) {
            mUsername = username;
            mPassword = password;
        }

        @Override
        protected Boolean doInBackground(Void... params) {

            try { // Simulate network access.
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                return false;
            }

            for (String credential : DUMMY_CREDENTIALS) {
                String[] pieces = credential.split(":");
                if (pieces[0].equals(mUsername)) {
                    // Account exists, return true if the password matches.
                    return pieces[1].equals(mPassword);
                }
            }

            return true;
        }

        @Override
        protected void onPostExecute(final Boolean success) {
            mAuthTask = null;
            showProgress(false);

            if (success) {
                //finish();
                Intent mainpageIntent = new Intent(LoginActivity.this, NavigationActivity.class);
                LoginActivity.this.startActivity(mainpageIntent);
            } else {
                mPasswordView.setError(getString(R.string.error_incorrect_password));
                mPasswordView.requestFocus();
            }
        }

        @Override
        protected void onCancelled() {
            mAuthTask = null;
            showProgress(false);
        }
    }