Swift 3代码

var activeField: UITextField?

override func viewDidLoad() {
    super.viewDidLoad()

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

func textFieldDidBeginEditing(_ textField: UITextField){
    activeField = textField
}

func textFieldDidEndEditing(_ textField: UITextField){
    activeField = nil
}

func keyboardWillShow(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if (self.activeField?.frame.origin.y)! >= keyboardSize.height {
            self.view.frame.origin.y = keyboardSize.height - (self.activeField?.frame.origin.y)!
        } else {
            self.view.frame.origin.y = 0
        }
    }
}

func keyboardWillHide(notification: NSNotification) {
    self.view.frame.origin.y = 0
}

移动视图的原点是一种幼稚的方法。

这里有一个更好的解决方案:当键盘出现时调整视图的高度。

let viewHeight = self.view.frame.height

    override func viewDidLoad() {
        super.viewDidLoad()

        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: UIResponder.keyboardWillShowNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: UIResponder.keyboardWillHideNotification, object: nil)
    }

    @objc func keyboardWillShow(notification: NSNotification) {
        if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
            if self.view.frame.height == self.viewHeight{
                self.view.frame = CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height - keyboardSize.height)
            }

        }
    }

    @objc func keyboardWillHide(notification: NSNotification) {
        if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {

            self.view.frame = CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height + keyboardSize.height)
        }
    }

斯威夫特4:

我有一个问题与最接受的答案，其中隐藏键盘并没有返回视图一直到页面的底部(只是部分)。这对我来说很有效(+为Swift 4更新)。

override func viewDidLoad() {
    super.viewDidLoad()
    self.hideKeyboardWhenTappedAround()
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
}

@objc func keyboardWillShow(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y == 0{
            self.view.frame.origin.y -= keyboardSize.height
        }
    }
}

@objc func keyboardWillHide(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y != 0{
            self.view.frame.origin.y = 0
        }
    }
}

斯威夫特4.1

 override func viewDidLoad() {
    super.viewDidLoad()            
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil)    
}

@objc func keyboardWillShow(notification: NSNotification) {        
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y == 0 {
            self.view.frame.origin.y -= keyboardSize.height   //can adjust as keyboardSize.height-(any number 30 or 40)
        }
    }        
}

@objc func keyboardWillHide(notification: NSNotification) {
    if self.view.frame.origin.y != 0 {
        self.view.frame.origin.y = 0
    }
}

如果你在同一个VC中有2个或更多的文本字段，用户点击其中一个，然后点击另一个，不调用keyboardWillHide函数，视图会再向上一次，这是不必要的，因为你会有键盘，一个空格，它有键盘的高度，然后视图，使用我编辑的答案中的代码:

override func viewDidLoad() {       
    super.viewDidLoad()
    NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillShow:"), name: UIKeyboardWillShowNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillHide:"), name: UIKeyboardWillHideNotification, object: nil)
}

func keyboardWillShow(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
        self.view.frame.origin.y -= keyboardSize.height
    }
}

func keyboardWillHide(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
        self.view.frame.origin.y += keyboardSize.height
    }
}

为了解决这个问题，将两个函数"KeyboardWillShow/Hide"替换为:

func keyboardWillShow(notification: NSNotification) {
 if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
    if view.frame.origin.y == 0{
        self.view.frame.origin.y -= keyboardSize.height
        }
    }
}

func keyboardWillHide(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
        if view.frame.origin.y != 0 {
            self.view.frame.origin.y += keyboardSize.height
        }
    }
}

类似于@Boris的回答，但在Swift 5中:

override func viewDidLoad() {
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: UIResponder.keyboardWillHideNotification, object: nil)
}

@IBAction func keyboardWillShow(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y == 0 {
            self.view.frame.origin.y -= keyboardSize.height
        }
    }
}

@IBAction func keyboardWillHide(notification: NSNotification) {
    if self.view.frame.origin.y != 0 {
        self.view.frame.origin.y = 0
    }
}