private static void closeMapFileQuietly(final MapFile mapFile) {
        if (mapFile != null) {
            mapFile.close();
        }
    }
Tries to open given uri as a mapfile.
If mapfile is invalid in any way (not available, not readable, wrong version, ...), then null is returned.
If mapfile is valid, then its attribution is read and returned (or a default attribution value in case attribution is null)
main/src/main/java/cgeo/geocaching/maps/mapsforge/MapsforgeMapProvider.java