Question 69348 in IOS Swift Question posted in
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Crash: Trying to complete an interactive gesture but the animation coordinator is nil – Ios swift

Recently a crash popped up in Firebase Crashlytics and I have no clue what it means. The message says:

Fatal Exception: NSInternalInconsistencyException
Trying to complete an interactive gesture but the animation coordinator is nil! (gesture=<_UIBarPanGestureRecognizer: 0x109f177c0; state = Ended; view = <UILayoutContainerView 0x1059153a0>; target= <(action=_gestureRecognizedInteractiveHide:, target=<UINavigationController 0x106837800>)>> action=Show)

and the stack trace looks like this:

    Fatal Exception: NSInternalInconsistencyException
0  CoreFoundation                 0x9904c __exceptionPreprocess
1  libobjc.A.dylib                0x15f54 objc_exception_throw
2  Foundation                     0x1306cc _userInfoForFileAndLine
3  UIKitCore                      0x918cec -[UINavigationController _gestureRecognizedInteractiveHide:]
4  UIKitCore                      0x1e042c -[UIGestureRecognizerTarget _sendActionWithGestureRecognizer:]
5  UIKitCore                      0x1a9560 _UIGestureRecognizerSendTargetActions
6  UIKitCore                      0x172260 _UIGestureRecognizerSendActions
7  UIKitCore                      0x1ab910 -[UIGestureRecognizer _updateGestureForActiveEvents]
8  UIKitCore                      0x163ad0 _UIGestureEnvironmentUpdate
9  UIKitCore                      0x1978c8 -[UIGestureEnvironment _updateForEvent:window:]
10 UIKitCore                      0x1a4a68 -[UIWindow sendEvent:]
11 UIKitCore                      0x354318 -[UIApplication sendEvent:]
12 UIKitCore                      0x177c30 __dispatchPreprocessedEventFromEventQueue
13 UIKitCore                      0x16ca1c __processEventQueue
14 UIKitCore                      0xfae7dc updateCycleEntry
15 UIKitCore                      0x7dd7d8 _UIUpdateSequenceRun
16 UIKitCore                      0xe57008 schedulerStepScheduledMainSection
17 UIKitCore                      0xe565f8 runloopSourceCallback
18 CoreFoundation                 0xbb020 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__
19 CoreFoundation                 0xcbce0 __CFRunLoopDoSource0
20 CoreFoundation                 0x5fe8 __CFRunLoopDoSources0
21 CoreFoundation                 0xb7f4 __CFRunLoopRun
22 CoreFoundation                 0x1f3b8 CFRunLoopRunSpecific
23 GraphicsServices               0x138c GSEventRunModal
24 UIKitCore                      0x5196a8 -[UIApplication _run]
25 UIKitCore                      0x2987f4 UIApplicationMain
26 libswiftUIKit.dylib            0x31184 UIApplicationMain(_:_:_:_:)
27 MYAPPNAME                      0x7220 main (MyAppStruct.swift)
28 ???                            0x104bb9a24 (Missing)

The MyAppStruct.swift is the only file in the trace that comes from my source code. It is just a struct which holds data and has some static methods for calculations. There is absolutely no relation with gestures and animations in this struct.

This only happened on iOS 15.1.1 devices (iPhone 12 and iPhone 13 Pro) for now.

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2

Answers


  1. Chosen as BEST ANSWER
    0

    I've managed to constantly reproduce this on an iPad 10.2 (9th gen). In my view controller, I have a scroll view as the top-most view in the hierarchy, and I was hiding/showing the navigation bar using the navigationController?.hidesBarsOnSwipe property. This property was set to true only when the scrollView's contentSize.height was greater than the view.bounds.height. The idea is to hide the navigation bar if the content scrolls, otherwise leave it visible and ignore the swipe gesture.

    The issue only occurred when the scrollView's contentSize.height was just about 50pt larger than the view.height, which happens really, really rarely.

    I removed the navigationController?.hidesBarsOnSwipe and used the scrollViewDidScroll method instead:

    extension HomeViewController: UIScrollViewDelegate {
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        if scrollView.contentOffset.y <= 10 {
            // scroll up
            navigationController?.setNavigationBarHidden(false, animated: true)
        } else if scrollView.contentOffset.y >= 10 {
            // scroll down
            navigationController?.setNavigationBarHidden(true, animated: true)
        }
    }
}

  2. 0

    FYI, I have a bug scenario that shows a similarly weird traceback (GUI event dispatched from inside UIKit’s update cycle!?), and I have posted a report to Apple Developer Forums here:
    https://developer.apple.com/forums/thread/699670

    I don’t think this is the "normal" way for GUI events to be dispatched. Seems hardly surprising that things could go wrong in the event handler.

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