umair151 umair151 - 7 months ago 46
Swift Question

UITapGestureRecognizer crashes on multiple taps

I am adding

UIImageView
into
UIScrollView
programmatically and adding a tap gesture on imageView. It recognizes the tap event exactly 4 times and on fourth time it crashes without any clear error message. This is in the controller named FeaturedListingDetailVC

Code:

let frame = CGRect(x: 0, y: 0, width: 128, height: 128)
_iv = UIImageView(frame: frame)
_iv.image = UIImage(named: "no_media")
_iv.userInteractionEnabled = true

tapGesture = UITapGestureRecognizer(target: self, action: #selector(initImagePopup(_:)))
_iv.addGestureRecognizer(tapGesture)

_iv.widthAnchor.constraintEqualToConstant(CGFloat.init(128)).active = true
_iv.heightAnchor.constraintEqualToConstant(CGFloat.init(128)).active = true
hrScroll.addSubview(_iv)


Function Called on Tap:

@objc func initImagePopup(gesture: UITapGestureRecognizer) {
print("I am tapped!!!")
}


Moreover, the way I load my target viewController (i.e. FeaturedListingDetailVC) really matters but I don't know why and how. Because when I push my target viewController into
UINavigationViewController
, it crashes on the first tap otherwise when I initialize target VC by presentation viewController it crashes on the 4th tap.

Crashes on First Tap When Initialized With Following Code:

let storyboard = UIStoryboard(name: "Post", bundle: nil)
let featuredVC = storyboard.instantiateViewControllerWithIdentifier("FeaturedListingDetailVC") as! FeaturedListingDetailVC
self.vc?.navigationController!.pushViewController(featuredVC, animated: true)


Crashes on 4th Tap When Initialized With Following Code:

let storyboard = UIStoryboard(name: "Post", bundle: nil)
let featuredVC = storyboard.instantiateViewControllerWithIdentifier("FeaturedListingDetailVC") as! FeaturedListingDetailVC
self.vc?.navigationController!.presentViewController(featuredVC, animated: true, completion: nil)


Backtrace:

* thread #1: tid = 0x78c3e, 0x0000000106365553 UIKit\`-[UIViewController(UIKitManual) release] + 122, queue = 'com.apple.main-thread', stop reason = EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
frame #0: 0x0000000106365553 UIKit\`-[UIViewController(UIKitManual) release] + 122
frame #1: 0xfffffffee7368160
frame #2: 0x0000000105bf72f3 UIKit\`-[UIViewController setChildModalViewController:] + 248
frame #3: 0x0000000105be853e UIKit\`-[UIViewController dealloc] + 1329
frame #4: 0x0000000105f48b31 UIKit\`_UIGestureRecognizerSendTargetActions + 162
frame #5: 0x0000000105f4519a UIKit\`_UIGestureRecognizerSendActions + 162
frame #6: 0x0000000105f43197 UIKit\`-[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 843
frame #7: 0x0000000105f4b655 UIKit\`___UIGestureRecognizerUpdate_block_invoke898 + 79
frame #8: 0x0000000105f4b4f3 UIKit\`_UIGestureRecognizerRemoveObjectsFromArrayAndApplyBlocks + 342
frame #9: 0x0000000105f38e75 UIKit\`_UIGestureRecognizerUpdate + 2634
frame #10: 0x0000000105ac548e UIKit\`-[UIWindow _sendGesturesForEvent:] + 1137
frame #11: 0x0000000105ac66c4 UIKit\`-[UIWindow sendEvent:] + 849
frame #12: 0x0000000105a71dc6 UIKit\`-[UIApplication sendEvent:] + 263
frame #13: 0x0000000105a4b553 UIKit\`_UIApplicationHandleEventQueue + 6660
frame #14: 0x00000001046f2301 CoreFoundation\`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
frame #15: 0x00000001046e822c CoreFoundation\`__CFRunLoopDoSources0 + 556
frame #16: 0x00000001046e76e3 CoreFoundation\`__CFRunLoopRun + 867
frame #17: 0x00000001046e70f8 CoreFoundation\`CFRunLoopRunSpecific + 488
frame #18: 0x000000010bf6ead2 GraphicsServices\`GSEventRunModal + 161
frame #19: 0x0000000105a50f09 UIKit\`UIApplicationMain + 171
* frame #20: 0x0000000103e34b22 JaClassified\`main + 114 at AppDelegate.swift:5
frame #21: 0x000000010886b92d libdyld.dylib\`start + 1
frame #22: 0x000000010886b92d libdyld.dylib\`start + 1

Answer

Sounding strange, I've tested a lot your code, and there is no way, always crashes.

So I simply tried changing name of callback method:

 func didTapOnImagePopup(recognizer: UITapGestureRecognizer) {}

And it works.

I really don't know why and I can find any reasonable explanation.

The only thing that I can think is that should exists an internal function called "initImagePopup".. but it's strange.

I'm really curious on the real explanation, if someone know it.