iOS:在扩展中从 NSNotificationCenter 返回值(swift)

Question

在我的扩展中，我以这种方式放置键盘通知的控件

protocol KeyboardSpaceProtocol {
    func addObservers()
    func removeObservers()
    func keyboardWillShow(notification:NSNotification) -> CGFloat
}

extension UIView: KeyboardSpaceProtocol {

    func addObservers() {
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(keyboardWillShow), name: UIKeyboardWillShowNotification, object: nil)
    }

    func removeObservers() {
        NSNotificationCenter.defaultCenter().removeObserver(self)
    }

    func keyboardWillShow(notification:NSNotification) -> CGFloat {
        let userInfo:NSDictionary = notification.userInfo!
        let keyboardFrame:NSValue = userInfo.valueForKey(UIKeyboardFrameEndUserInfoKey) as! NSValue
        let keyboardRectangle = keyboardFrame.CGRectValue()
        return keyboardRectangle.height
    }
}

现在我想更新 UIView 类中的 CGFloat 值 (keyboardheight)...如何在 View Controller 中更新？我不知道键盘何时熄灭以及如何更新我的值。有什么建议吗？

Answer 1

您可以使用objc_linkedObject在运行时添加属性。

我的示例使用 UIViewController 而不是 UIView 只是因为它对我来说似乎更合乎逻辑。

import Foundation
import UIKit
import ObjectiveC

protocol KeyboardSpaceProtocol {
    func addObservers()
    func removeObservers()
    func keyboardWillShow(notification:NSNotification) -> CGFloat
    var keyBoardHeight: CGFloat {get set}
}

private var keyBoardKey: UInt8 = 0
extension  UIViewController: KeyboardSpaceProtocol {

    var keyBoardHeight: CGFloat {
        get {
            return objc_getAssociatedObject(self, &keyBoardKey) as! CGFloat
        }
        set { objc_setAssociatedObject(self, &keyBoardKey, newValue,  objc_AssociationPolicy(rawValue: 0)!) }
    }

    func addObservers() {
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(UIViewController.keyboardWillShow(_:)), name: UIKeyboardWillShowNotification, object: nil)
    }

    func removeObservers() {
        NSNotificationCenter.defaultCenter().removeObserver(self)
    }

    func keyboardWillShow(notification:NSNotification) -> CGFloat {
        let userInfo:NSDictionary = notification.userInfo!
        let keyboardFrame:NSValue = userInfo.valueForKey(UIKeyboardFrameEndUserInfoKey) as! NSValue
        let keyboardRectangle = keyboardFrame.CGRectValue()

        var selfAsProtocol = self as KeyboardSpaceProtocol
        selfAsProtocol.keyBoardHeight = keyboardRectangle.height

        return keyboardRectangle.height
    }
}