How to download osmdroid tiles on user end?

Question

I already successful to load map tiles from SD Card of osmdroid (Mapnik)

But now i want to give a option in my android app to download map tile that user want to use mean map show online user select a specific area and cashes it for his use i don't know how to do please help thanks

Answer 1

I am not sure where the question points to. As far as I understand it, you have the user select an area - which is expressed in geographical coordinates - and then use these coordinates to calculate the tiles to be retrieved.

Under Slippy map tilenames in the OSM wiki there is a very good explanation how to do this:

• Reproject the coordinates to the Mercator projection (from EPSG:4326 to EPSG:3857):

  x = lon
  y = arsinh(tan(lat)) = log[tan(lat) + sec(lat)]
  

  (lat and lon are in radians)

• Transform range of x and y to 0 – 1 and shift origin to top left corner:

  x = [1 + (x / π)] / 2
  y = [1 − (y / π)] / 2
  

• Calculate the number of tiles across the map, n, using 2^zoom
• Multiply x and y by n. Round results down to give tilex and tiley.