question: public static OsmMBTileSource createFromFile ( File file ) { SQLiteDatabase db ; int flags = SQLiteDatabase . NO_LOCALIZED_COLLATORS | SQLiteDatabase . OPEN_READONLY ; int value ; int minZoomLevel ; int maxZoomLevel ; int tileSize = tileSizePixels ; InputStream is = null ; db = SQLiteDatabase . openDatabase ( file . getAbsolutePath ( ) , null , flags ) ; value = getInt ( db , "SELECT MIN(zoom_level) FROM tiles;" ) ; minZoomLevel = value > - 1 ? value : minZoom ; value = getInt ( db , "SELECT MAX(zoom_level) FROM tiles;" ) ; maxZoomLevel = value > - 1 ? value : maxZoom ; Cursor cursor = db . rawQuery ( "SELECT tile_data FROM images LIMIT 0,1" , new String [ ] { } ) ; if ( cursor . getCount ( ) != 0 ) { cursor . moveToFirst ( ) ; is = new ByteArrayInputStream ( cursor . getBlob ( 0 ) ) ; Bitmap bitmap = BitmapFactory . decodeStream ( is ) ; tileSize = bitmap . getHeight ( ) ; Log . w ( t , String . format ( "Found a tile size of %d" , tileSize ) ) ; } cursor . close ( ) ; return new OsmMBTileSource ( minZoomLevel , maxZoomLevel , tileSize , file , db ) ; }
target:  Creates a new MBTileSource from file. Parameters minZoom, maxZoom en tileSizePixels are obtained from the database. If they cannot be obtained from the DB, the default values as defined by this class are used.