未显示键盘时调用 KeyboardDidShow答案

【问题标题】：KeyboardDidShow called when keyboard isn't shown未显示键盘时调用 KeyboardDidShow
【发布时间】：2018-09-24 00:13:12
【问题描述】：

所以我使用 KeyboardDidShow 设置了键盘观察器，这样我就可以仅在显示键盘时向上移动视图。但是，KeyboardDidShow 在每个视图启动时运行，并且在随机时间运行。我尝试过监控键盘框架，并且仅在框架发生变化时才移动视图，但是即使没有显示键盘，视图也会经常发生变化。通常，每当首次启动视图时都会发生这种情况，因此我尝试添加延迟，但它不是很可靠。

DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
        NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardDidShow(_:)), name: NSNotification.Name.UIKeyboardDidShow, object: nil)
    }

@objc func keyboardDidShow(_ notification: Notification) {

    let userInfo = notification.userInfo!
    let beginFrameValue = (userInfo[UIKeyboardFrameBeginUserInfoKey] as? NSValue)!
    let beginFrame = beginFrameValue.cgRectValue
    let endFrameValue = (userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue)!
    let endFrame = endFrameValue.cgRectValue

    if beginFrame.equalTo(endFrame) {
        return
    } else {
        let indexPath = IndexPath(item: 0, section: 0)
        if UIScreen.main.bounds.height == 812 {
            collectionView?.contentInset = UIEdgeInsets(top: 318 + view.safeAreaInsets.bottom, left: 0, bottom: 73, right: 0)
        } 
        collectionView?.scrollToItem(at: indexPath, at: .bottom, animated: true)
    }
}

【问题讨论】：

你最好只使用keyboardDidChangeFrameNotification。它还将通知 kb 几何图形随动画持续时间的变化。当键盘即将显示/隐藏以及旋转设备时调用它
我尝试使用keyboardDidChangeFrame，但只要第一次显示视图，它仍然会运行。我在某处读到它们在开始时运行，因为当时（或类似）配置了键盘的框架

标签： swift keyboard

【解决方案1】：

问题是您配置了错误的通知。不要使用 UIKeyboardDidShow。使用 UIKeyboardWillShow，并检查旧框架、新框架以及新框架是否会覆盖您的视图。

实现一个健壮的实现并非易事，但它肯定是一个之前已解决的问题，已在此处多次解释。

【讨论】：

【解决方案2】：

对于 UIViewController 实例，仅当视图可见且不订阅通知多次时，您才需要观察这些通知。最好的方法是：

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)        
    NotificationCenter.default.addObserver(self, selector: #selector(onKeyboardWillChangeFrame(_:)), name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
}

这是我项目中用于处理键盘框架的工作代码

@objc private func onKeyboardWillChangeFrame(_ notification: NSNotification) {
    // extract values
    if let userInfo = notification.userInfo,
        let keyboardFrameEnd = (userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue,
        let animationCurveInt = (userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? NSNumber)?.intValue {

        /*
         СУКАБЛЯТЬ
         With upgrate to Swift 4.2 UIView.AnimationCurve(rawValue: 7) returns actual instance of
         UIView.AnimationCurve which crashes on access, mod by 4 limits value to max
         */
        let animationCurve = UIView.AnimationCurve(rawValue: animationCurveInt % 4) ?? .easeIn

        // View chanages
        let topPoint = self.view.convert(keyboardFrameEnd.origin, from: self.view.window)
        let height = self.view.bounds.size.height - topPoint.y

        ... update your constraints or manually update vars that affect layoutSubviews()...

        let animationDuration: TimeInterval = (userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? NSNumber)?.doubleValue ?? 0
        var animationOptions: UIView.AnimationOptions = []
        switch animationCurve {
            case .easeInOut: animationOptions = .curveEaseInOut
            case .easeIn: animationOptions = .curveEaseIn
            case .easeOut: animationOptions = .curveEaseOut
            case .linear: animationOptions = .curveLinear
        }

        // run animation
        UIView.animate(withDuration: animationDuration, delay: 0, options: animationOptions, animations: {
            self.view.layoutIfNeeded()
        })
    }
}

【讨论】：