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

        private final String mEmail;
        private final String mPassword;

        UserLoginTask(String email, String password) {
            mEmail = email;
            mPassword = password;
        }

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

        return checkLoginCredentials();
        //return true;
        }

        public Boolean checkLoginCredentials() {

            for (Map<String, Object> mapOfUsers : usersList) {
                for(Map.Entry<String, Object> user : mapOfUsers.entrySet()) {
                    String key = user.getKey();
                    String value = (String) user.getValue();
                    if(mEmail.equals(key) && mPassword.equals(value)) {
                        return true;
                    }
                }
            }
            return false;
        }

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

            if (success) {
                finish();
                Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                intent.putExtra("loggedEmail", mEmail);
                startActivity(intent);
            } else {
                mPasswordView.setError(getString(R.string.error_incorrect_password));
                mPasswordView.requestFocus();
            }
        }

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

    }