code: public static TileCache createTileCache(File cacheDir, String id, int tileSize,
                                              int width, int height, double overdraw, boolean persistent) {
          int cacheSize = getMinimumCacheSize(tileSize, overdraw, width, height);
          return createExternalStorageTileCache(cacheDir, id, cacheSize, tileSize, persistent);
      }
docs: Utility function to create a two-level tile cache with the right size, using the size of the map view.
  
  @param cacheDir   the cache directory
  @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
  @param persistent whether the cache should be persistent
  @return a new cache created on the external storage