Delay with UI Related Code

[dlallie]

As part of the implementation for this issue, another bug has been introduced.

Something very strange is now happening with some UI code when run from the scanView(_ scanView: ScanView, didDetectScannables scannables: [Scannable]) callback method. For example, calling the present method to show a new view controller takes >1 second for the app to respond.

I've used Instruments to profile my app and it seems that for some reason, even when the UI code is called in a DispatchQueue.main.async block, the main thread is idling and does no work for a period of time. Perhaps the main thread is being put to sleep at some point by Quikkly? And identical project configuration works fine with version 3.4.5.

[janekp]

It appears to be an old issue that was fixed. A regression. present+dismiss combination is an old iOS quirk where somehow animated transitions can block unrelated code. I’m afk and can (re-)fix it next month.

[malikk77]

hello there? i have some related issue where i can not present my view controller after qrcode scan. i try to pause the scanner and then run in Dispatchque as well but it stuck. if i use without pausing it doesnt do anything.

//MARK:- Delegate Methods Below

func scanView(_ scanView: ScanView, didDetectScannables scannables: [Scannable]) {
if let scannable = scannables.first {
DispatchQueue.main.async {
let vc = PostCommentsVC()
vc.postId = Int(String(700))
vc.modalPresentationStyle = .currentContext
vc.modalTransitionStyle = .coverVertical
self.present(vc, animated: true)
}
print("Found scannable code: (scannable.value)")
}
}

[dlallie]

@malikk77 Yes this issue cropped up again in some past release of the SDK

I was able to work around it by running a UIView animation block to delay the view controller presentation and then proceeding. Whatever the nature of this bug running an animation set causes the view controller presentations to then work correctly:

UIView.animate(withDuration: 0.3, animations: { self.view.alpha = 0.995 }) { _ in self.present(toPresent, animated: true, completion: null) }

Note that I’m animating the view alpha here because some property has to change for the animation to actually run