[iPhone][UITableView]How to know when a group complete replace other (by scroll)?

Question

Please refer to bellow image to get detail:

I think, UITableView has some events occur when scrolling em when a group complete replace other, but I don't know :(

Answer 1

You can get drawing rectangle for each section using -rectForSection method (see "Accessing Drawing Areas of the Table View" part in UITableView docs). Then in your UITableViewDelegate implementation you can track scrolling events in table view, e.g. in -scrollViewDidScroll: method you can compare current contentsOffset and origin point of the rectangle for each section to determine which section is active at the moment.