使用单例代理管理键盘

当我第一次开始管理键盘时，我会在每个 ViewController 中使用单独的 Notifications。

通知方法（使用 NSNotification）：

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(ViewController.keyboardNotification(_:)), name: UIKeyboardWillChangeFrameNotification, object: nil)
    }

    func keyboardNotification(notification: NSNotification) {
        guard let userInfo = notification.userInfo else { return }
    
        let endFrame = (userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.CGRectValue()
        let duration: NSTimeInterval = (userInfo[UIKeyboardAnimationDurationUserInfoKey] as? NSNumber)?.doubleValue ?? 0
        let animationCurveRawNSN = userInfo[UIKeyboardAnimationCurveUserInfoKey] as? NSNumber
        let animationCurveRaw = animationCurveRawNSN?.unsignedLongValue ?? UIViewAnimationOptions.CurveEaseOut.rawValue
        let animationCurve: UIViewAnimationOptions = UIViewAnimationOptions(rawValue: animationCurveRaw)
    
        if endFrame?.origin.y >= UIScreen.mainScreen().bounds.size.height {
            lowerViewBottomConstraint.constant = 0
        } else {
            lowerViewBottomConstraint.constant = endFrame?.size.height ?? 0.0
        }
        view.animateConstraintWithDuration(duration, delay: NSTimeInterval(0), options: animationCurve, completion: nil)
    }
}

我的问题是我发现自己一次又一次地为每一个 ViewController 编写这个代码。在尝试了一下后，我发现使用 Singleton + Delegate 模式允许我重用一堆代码并在一个地方组织所有的键盘管理！

单例+代表方法：

protocol KeyboardManagerDelegate: class {
    func keyboardWillChangeFrame(endFrame: CGRect?, duration: NSTimeInterval, animationCurve: UIViewAnimationOptions)
}

class KeyboardManager {

    weak var delegate: KeyboardManagerDelegate?

    class var sharedInstance: KeyboardManager {
        struct Singleton {
            static let instance = KeyboardManager()
        }
        return Singleton.instance
    }

    init() {
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(KeyboardManager.keyboardWillChangeFrameNotification(_:)), name: UIKeyboardWillChangeFrameNotification, object: nil)
    }

    @objc func keyboardWillChangeFrameNotification(notification: NSNotification) {
        guard let userInfo = notification.userInfo else { return }
    
        let endFrame = (userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.CGRectValue()
        let duration: NSTimeInterval = (userInfo[UIKeyboardAnimationDurationUserInfoKey] as? NSNumber)?.doubleValue ?? 0
        let animationCurveRawNSN = userInfo[UIKeyboardAnimationCurveUserInfoKey] as? NSNumber
        let animationCurveRaw = animationCurveRawNSN?.unsignedLongValue ?? UIViewAnimationOptions.CurveEaseOut.rawValue
        let animationCurve: UIViewAnimationOptions = UIViewAnimationOptions(rawValue: animationCurveRaw)
    
        delegate?.keyboardWillChangeFrame(endFrame, duration: duration, animationCurve: animationCurve)
    }
}

现在，当我想从 ViewController 管理键盘时，我需要做的就是将委托设置为该 ViewController 并实现任何委托方法。

class ViewController: UIViewController {
    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)
        KeyboardManager.sharedInstance.delegate = self
    }
}

// MARK: - Keyboard Manager

extension ViewController: KeyboardManagerDelegate {
    func keyboardWillChangeFrame(endFrame: CGRect?, duration: NSTimeInterval, animationCurve: UIViewAnimationOptions) {
        if endFrame?.origin.y >= UIScreen.mainScreen().bounds.size.height {
           lowerViewBottomConstraint.constant = 0
        } else {
            lowerViewBottomConstraint.constant = (endFrame?.size.height ?? 0.0)
        }
        view.animateConstraintWithDuration(duration, delay: NSTimeInterval(0), options: animationCurve, completion: nil)
    }
}

这种方法也很容易定制！ 假设我们想为 UIKeyboardWillHideNotification 添加功能。这就像为我们的 KeyboardManagerDelegate 添加方法一样简单。

KeyboardManagerDelegate with UIKeyboardWillHideNotification：

protocol KeyboardManagerDelegate: class {
    func keyboardWillChangeFrame(endFrame: CGRect?, duration: NSTimeInterval, animationCurve: UIViewAnimationOptions)
    func keyboardWillHide(notificationUserInfo: [NSObject: AnyObject])
}

class KeyboardManager {
    init() {
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(KeyboardManager.keyboardWillChangeFrameNotification(_:)), name: UIKeyboardWillChangeFrameNotification, object: nil)
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(KeyboardManager.keyboardWillHide(_:)), name: UIKeyboardWillHideNotification, object: nil)
    }

    func keyboardWillHide(notification: NSNotification) {
        guard let userInfo = notification.userInfo else { return }
        delegate?.keyboardWillHide(userInfo)
    }
}

假设我们只想在一个 ViewController 中实现 func keyboardWillHide(notificationUserInfo: [NSObject: AnyObject])。我们也可以选择这个方法。

typealias KeyboardManagerDelegate = protocol<KeyboardManagerModel, KeyboardManagerConfigureable>

protocol KeyboardManagerModel: class {
    func keyboardWillChangeFrame(endFrame: CGRect?, duration: NSTimeInterval, animationCurve: UIViewAnimationOptions)
}

@objc protocol KeyboardManagerConfigureable {
    optional func keyboardWillHide(userInfo: [NSObject: AnyObject])
}

*注意这种模式有助于避免过度使用 @objc。有关详细信息，请访问 http://www.jessesquires.com/avoiding-objc-in-swift/ ！

总之，我发现使用 Singleton + Delegate 来管理键盘比使用 Notifications 更高效，更容易使用