private static MapFile createMapFile(final String mapFileCtx, final InputStream fis) {

        if (fis != null) {
            try {
                return new MapFile((FileInputStream) fis, 0, Settings.getMapLanguage());
            } catch (MapFileException mfe) {
                Log.e("Problem opening map file '" + mapFileCtx + "'", mfe);
            }
        }
        return null;
    }
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