private void setUserDefinedTileProviderUriSummary(final String uri) {
        SettingsUtils.setPrefSummary(this, R.string.pref_userDefinedTileProviderUri, getString(R.string.settings_userDefinedTileProviderUri) + "\n\n" + uri);
    }
Fill the choice list for map sources.
main/src/main/java/cgeo/geocaching/settings/fragments/PreferenceMapSourcesFragment.java