Swift 3: UITapGestureRecognizer Not Firing - ios

Question

I'm not sure why but my UITapGestureRecognizer is not firing correctly. Well in fact it is not firing at all. I am trying to get a function to run on the tap of an image.
Info about the setup:
Not using storyboards, loading everything programmatically
The view that I am loading this on also has a UICollectionView on it
ok so for the code:
The UIImageView is declared like so:
let backButtonIcon: UIImageView = {
let bbi = UIImageView()
bbi.image = UIImage(named: "backIcon")
bbi.translatesAutoresizingMaskIntoConstraints = false
bbi.layer.zPosition = 2
return bbi
}()
I then added that to the view:
view.addSubview(backButtonIcon)
to add the tap functionality to the UIImageView I am using:
let tapBackButton = UITapGestureRecognizer(target: self, action: #selector(backButtonPressed))
backButtonIcon.isUserInteractionEnabled = true
backButtonIcon.addGestureRecognizer(tapBackButton)
and lastly, here is the function that I am trying to run, just a simple print at the moment:
func backButtonPressed(sender: UITapGestureRecognizer) {
print("Go Back Pressed")
}
Update:
I have already tried adding:
bbi.isUserInteractionEnabled = true
and also:
backButtonIcon.isUserInteractionEnabled = true
Update 2:
I created another blank view and used the code exactly as it is here and it worked.
Could it be something to do with the UICollectionView?
I made the UICollectionView zPosition -1 and the UIImageView zPosition at 1 but that alas that also did not work.

Answer 1

Image views ignore user events by default. Normally, you use image views only to present visual content in your interface. If you want an image view to handle user interactions as well, change the value of its isUserInteractionEnabled property to true. After doing that, you can attach gesture recognizers or use any other event handling techniques to respond to touch events or other user-initiated events.
source: https://developer.apple.com/reference/uikit/uiimageview

Answer 2

I think the issue is with the UICollectionView, which is composed of UICollectionViewCells that already have a tap enabled by definition.
I'm looking through a very old app (Swift 1.x) I wrote for my personal usage (as in it never saw the light of day) and here's what I seemed to do - you probably need to do some variation of this:
Subclassed UICollectionViewCell and added a UILabel and UIImageView as subviews to it, populating them (along with a NSURL for the tap action).
Declared (and adopted) a specific UIViewController to also be my UICollectionView delegate (also for my purposes it was a SFSafariViewController delegate).
In that VC's viewDidLoad() I did set up a long press (for removing) and double tap (for reloading) gestures, but did not set up a tap gesture - it isn't needed.
In that VC's viewDidLoad() I loaded (and populated) the cells.
Here's the thing I think you are getting stuck on, but without more code I'm not sure:
Coded against:
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItemAtIndexPath(indexPath) as? BookmarkCell {
selectedBookmarkSection = indexPath.section
selectedBookmarkRow = indexPath.row
sfc = SFSafariViewController(URL: cell.targetUrl!, entersReaderIfAvailable:true)
sfc.delegate = self
presentViewController(sfc, animated: true, completion: nil)
} else {
// Error indexPath is not on screen: this should never happen.
}
}
Please be kind, as this was something I wrote back in July 2014! (I update the collectionView(didSelectItemAt:indexPath:) for Swift 3.x but that's it.)
TR;DR: I think - particularly if your tap is seen outside of a UICollectionView - that this may get you working.