get
Returns a Tile for the specified coordinates.
This method is called asynchronously when tiles are needed for rendering. Implementations should be thread-safe and non-blocking.
Return
Tile containing image data, or null if tile is not available
Parameters
x
Tile column (0 to 2^zoom - 1)
y
Tile row (0 to 2^zoom - 1)
zoom
Zoom level (0-19)