正确检测键盘的外观和消失

我有一个包含三个文本字段的注册屏幕：一个用于用户名，另外两个用于密码（安全文本输入） . 我已设置侦听器以确定键盘何时出现并消失以相应地移动我的视图，以便键盘不会阻止输入窗口小部件 .

在我的viewDidLoad（）中：

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

NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: NSNotification.Name.UIKeyboardDidHide, object: nil)

选择器功能：

@objc func keyboardWillShow(notification: NSNotification) {
    let userInfo = notification.userInfo
    var keyboardFrame:CGRect = (userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
    keyboardFrame = self.view.convert(keyboardFrame, from: nil)
    movement = (keyboardFrame.size.height/2 + 20)
    print("Keyboard Appeared with a height of \(movement) including 20 offset")
    UIView.animate(withDuration: 0.3, animations: {
        self.view.frame = self.view.frame.offsetBy(dx: 0, dy: self.movement * -1.0) //dy is negative for upward movement
    })
}

@objc  func keyboardWillHide(notification: NSNotification)               
    print("Keyboard Disappeared with a height of \(movement) offset included")
    UIView.animate(withDuration: 0.3, animations: {
        self.view.frame = self.view.frame.offsetBy(dx: 0, dy: self.movement)
    })
}

并且，将textfield委托设置为视图控制器，我有：

extension SignUpViewController: UITextFieldDelegate {

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if textField == textFieldUsername {
            textFieldPassword.becomeFirstResponder()
        } else if textField == textFieldPassword {
            textFieldPasswordConfirm.becomeFirstResponder()
       } else {
            textFieldPasswordConfirm.resignFirstResponder()
       }
       return true
    }
}

最后，我还有一个tap taplistener，用于确定用户点击屏幕上的任何位置以消除键盘 . 为此我用过：

view.endEditing(true)

当我点击文本字段时，会调用keyboardWillShow（），当我点击屏幕外的任何地方时，会调用keyboardWillHide（） . 这是预期的 .

但是，当我使用返回键从一个文本字段切换到另一个文本字段时，虽然键盘没有从屏幕上消失，但仍会调用keyboardWillShow（） .

此外，当我在文本字段中输入一些文本时，随机调用keyboardWillShow（） .

如何阻止这些不受欢迎的键盘通知？

EDIT

在阅读了@rmaddy和@Adam Eberbach的答案之后，我想出了不同的方法 . 首先，我为可滚动视图定义一个协议，并在视图控制器中实现它，我希望在其中具有滚动效果：

protocol ScrollableProtocol {
    var viewScrolled: Bool { get}
    func checkScroll()
    func performScroll(direction: Int)
}

然后在视图控制器中：

private var activeTextField: UITextField?
var isScrolled: Bool = false
let offset: CGFloat = 155.00 //for now I'm defining this value as a constant which is supposed to be less than the height of the keyboard

协议的实施：

extension SignUpViewController: ScrollableProtocol {

    var viewScrolled: Bool {
        get {
            return isScrolled
        }
    }

    func checkScroll() {
        if !viewScrolled {
            performScroll(direction: 0)
            isScrolled = !isScrolled
        } 
    }

    func registerTapListener() {
        let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(clearKeyboard))
        view.addGestureRecognizer(tap)
    }

    @objc func clearKeyboard() {
        activeTextField?.resignFirstResponder()
        if viewScrolled {
            performScroll(direction: 1)
            isScrolled = !isScrolled
        }
    }

    func performScroll(direction: Int) {
        //0 -> scroll up, 1 -> scroll down
        if direction == 0 {
            UIView.animate(withDuration: 0.3, animations: {
            self.view.frame = self.view.frame.offsetBy(dx: 0, dy: self.offset * -1)
            })
        } else if direction == 1 {
            UIView.animate(withDuration: 0.3, animations: {
            self.view.frame = self.view.frame.offsetBy(dx: 0, dy: self.offset)
            })
        }
    }
}

UITextField委托方法：

extension SignUpViewController: UITextFieldDelegate {

    func textFieldDidBeginEditing(_ textField: UITextField) {
        activeTextField = textField
        checkScroll()
    }

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if textField == textFieldUsername {
            textFieldPassword.becomeFirstResponder()
        } else if textField == textFieldPassword {
            textFieldPasswordConfirm.becomeFirstResponder()
        } else {
            textFieldPasswordConfirm.resignFirstResponder()
            performScroll(direction: 1)
            isScrolled = !isScrolled
        }
        return true
    }
}

最后，viewDidLoad方法：

override func viewDidLoad() {
    super.viewDidLoad()    
    registerTapListener()
    textFieldUsername.delegate = self
    textFieldPassword.delegate = self
    textFieldPasswordConfirm.delegate = self
}

这种方式是对的还是一种复杂的方法？