NSNotification.Name.UIKeyboardWillShow crash - Unable to find cause

问题

Users of my app have reported a random crash. I have integrated CrashAnalytics which is giving the following details :

__CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 20.

The line number indicated is 154, which is :

self.notesView.content.frame = CGRect(x: self.notesView.content.frame.origin.x, y: self.notesView.content.frame.origin.y, width: self.notesView.content.frame.size.width, height: self.notesView.content.frame.size.height - keyboardFrame.size.height).

Following is the code I have written which consist of this line :

override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        label_title.addObserver(self, forKeyPath: "contentSize", options: .new, context: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardShown), name:NSNotification.Name.UIKeyboardWillShow, object: nil);
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardHide), name:NSNotification.Name.UIKeyboardWillHide, object: nil);
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        label_title.removeObserver(self, forKeyPath: "contentSize")
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillShow, object: nil)
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillHide, object: nil)
    }

    func keyboardShown(notification: NSNotification) {
        let info = notification.userInfo!
        let keyboardFrame: CGRect = (info[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
        self.notesView.content.frame = CGRect(x: self.notesView.content.frame.origin.x, y: self.notesView.content.frame.origin.y, width: self.notesView.content.frame.size.width, height: self.notesView.content.frame.size.height - keyboardFrame.size.height)
    }

Firstly, this is quite random and I never get it. Secondly, I am not able to find exact cause for it. Is this because of notification observer or because of notesView (which is not nil).
As suggested here, should I remove keyboard notification observer in deinit ?
Please guide me through this if someone has experienced this previously.

回答1:

Change signature of your function to this

@objc func keyboardShown(_ notification: Notification)

来源：https://stackoverflow.com/questions/48478802/nsnotification-name-uikeyboardwillshow-crash-unable-to-find-cause

标签

ios

swift

nsnotificationcenter

crashlytics