public void initPreferences(final @XmlRes int preferenceResource, final String rootKey) {
        setPreferencesFromResource(preferenceResource, rootKey);
        checkExtendedSettingsVisibility(Settings.extendedSettingsAreEnabled() || this instanceof PreferencesFragmentRoot);
    }
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