我正在使用UIKeyboardFrameEndUserInfoKey键获取键盘高度,如下所示:

let keyboardHeight = (userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue.height
print(keyboardHeight)

如果我点击UITextView,键盘就会出现并打印
258.0

然后按⌘ + k,模拟器将连接硬件键盘,因此模拟器上的软件键盘将关闭。

如果我按⌘ + k再次组装键盘,键盘显示通知将被调用两次并打印
216.0
258.0

为什么键盘显示通知被调用两次,为什么首先使用216.0

更新

这是我的全部代码。
class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        let notificationCenter = NotificationCenter.default
        notificationCenter.addObserver(self, selector: #selector(ViewController.keyboardWillShow(notification:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
        notificationCenter.addObserver(self, selector: #selector(ViewController.keyboardWillHide(notification:)), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
    }

    @objc func keyboardWillShow(notification: NSNotification) {
        let userInfo = notification.userInfo!
        let keyboardHeight = (userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue.height

        print(keyboardHeight);
    }

    @objc func keyboardWillHide(notification: NSNotification) {

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

如果多次按⌘ + k,结果将显示出来...

result console image

最佳答案

不太确定如何声明observer,但是以下代码在Xcode 8和Xcode 9 beta(iOS 11)中都可以正常工作。

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

     NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name:NSNotification.Name.UIKeyboardWillShow, object: nil)
}

@objc func keyboardWillShow(sender: NSNotification) {
    let keyboardHeight = (sender.userInfo?[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue.height
    print(keyboardHeight)
}

更新:
刚刚测试了您的代码,它就可以正常工作,您还必须拥有其他干扰它的内容。

测试后的输出:
226.0
226.0
226.0
226.0
226.0
226.0

10-07 18:57
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