protected void setFlagForRestartRequired(final @StringRes int... prefKeyIds) {
        for (int prefKeyId : prefKeyIds) {
            PreferenceUtils.setOnPreferenceChangeListener(findPreference(getString(prefKeyId)), (preference, newValue) -> {
                setFlagForRestartRequired();
                return true;
            });
        }
    }
searches recursively in all elements of given prefGroup for first occurrence of s
returns found preference on success, null else
(prefers preference entries over preference groups)
main/src/main/java/cgeo/geocaching/settings/fragments/BasePreferenceFragment.java