title: Progressive download of images in a UITableView
body: <p>I'm developing on the iPhone and I have seen in the AppStore that the images are progressively downloaded in the UITableView... How can I implement that?
  My idea was to detect the showed content (which cells are shown) and download these images. My problem is that I don't know how to detect the showed cells!
  Is it the good way to do it?</p>
  
  <p>Best</p>