code: public static TileCache createTileCache(Context c, String id, int tileSize, int width, int height, double overdraw) {
          return createTileCache(c, id, tileSize, width, height, overdraw, false);
      }
docs: Utility function to create a two-level tile cache with the right size, using the size of the map view. This is
  the compatibility version that by default creates a non-persistent cache.
  
  @param c        the Android context
  @param id       name for the storage directory
  @param tileSize tile size
  @param width    the width of the map view
  @param height   the height of the map view
  @param overdraw overdraw allowance
  @return a new cache created on the external storage