选择UITableViewCell时出了什么问题？

When I select a UITableViewCell the background become gray, the the gray height is strange. Some of the cell is strange like it.I set seperator line style to none. And I add labels to the front and foot cell ,so there are lines between cell.As is show In the first picture. The other cells are normal as what I expect showed in the second picture.When I select a UITableViewCell the background