Use right to left UIScreenEdgePanGestureRecognizer on UITableView that has section indexes - ios

Question

I want to add a UIScreenEdgePanGestureRecognizer to a UITableView so that I can edge swipe from the right side to go to the next screen in my controller hierarchy.
This works fine except when the table view has section indexes shown on the side. In that case, the section index area handles the touches, so I can't swipe from the edge. I would like to be able to support both the edge pan and the section index tap and vertical pan functionality.
I tried adding a view on top of the UITableView to handle the swipe, but then that handles all touches and the table view no longer gets anything.

Answer 1

Okay, so I tried a bunch of stuff and came up with a non-ideal but working solution.
The first part of the problem is that the section index is in its own view as a subview of UITableView. So it captures any touches or gesture recognizers that you might add to the UITableView.
The second problem is that the section index view is not part of the public API.
So my solution is to add a UIScreenEdgePanGestureRecognizer to the section index view.
The view is an instance of the private class UITableViewIndex. To get it I created a UITableView extension:
extension UITableView {
var sectionIndexView: UIView? {
for view in self.subviews {
if view.className() == "UITableViewIndex" {
return view
}
}
return nil
}
}
NOTE the above code is fragile and not future proof, because if Apple changes the class name or its location in the view hierarchy it will no longer work. In my case the edge swipe is a convenience feature, and there is a "Next" button at the top of the screen. In addition, most of my view controllers don't have a table index, so if it stopped working it would only be on a few screens. So if this solution doesn't work in the future then it's not a huge deal.
I also wrote an convenience function to get the edge gesture recognizer from any view:
extension UIView {
var screenEdgePanGestureRecognizer: UIScreenEdgePanGestureRecognizer? {
guard let gestures = self.gestureRecognizers else {
return nil
}
for gesture in gestures {
if let edgePan = gesture as? UIScreenEdgePanGestureRecognizer {
return edgePan
}
}
return nil
}
}
I add a UIScreenEdgePanGestureRecognizer to the UITableView in the viewDidLoad method of my view controller.
Finally, in viewDidAppear of my view controller I check to see if the gesture recognizer has been added to the section index view. If it hasn't, then I add it there. You need to do this at some point after the section index has been added to the table view - i.e. not in viewDidLoad. And you need to make sure you're not adding the gesture recognizer multiple times.