private static File[] getMBTilesSources(final Context context) {
        return context.getExternalMediaDirs()[0].listFiles((dir, name) -> StringUtils.endsWith(name, FileUtils.BACKGROUND_MAP_FILE_EXTENSION));
    }
returns a list of .mbtiles files found in app-specific media folder, typically /Android/media/(app-id)/*.mbtiles
main/src/main/java/cgeo/geocaching/unifiedmap/layers/MBTilesLayerHelper.java