在Swift 4中，添加@objc:

在viewDidLoad中:

let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(self.dismissKeyboard))
view.addGestureRecognizer(tap)

功能:

@objc func dismissKeyboard() {
  view.endEditing(true)
}

因为我编辑的@King-Wizard的回答被拒绝了，所以发布了一个新的答案。

让你的类成为UITextField的委托并重写touchesBegan。

斯威夫特4

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet var textField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()
        textField.delegate = self
    }

    //Called when 'return' key is pressed. Return false to keep the keyboard visible.
    func textFieldShouldReturn(textField: UITextField) -> Bool {
        return true
    }

    // Called when the user clicks on the view (outside of UITextField).
    override func touchesBegan(touches: Set<UITouch>, with event: UIEvent?) {
        self.view.endEditing(true)
    }

}

override func viewDidLoad() {
    super.viewDidLoad()
          
    //Looks for single or multiple taps. 
     let tap = UITapGestureRecognizer(target: self, action: #selector(UIInputViewController.dismissKeyboard))

    //Uncomment the line below if you want the tap not not interfere and cancel other interactions.
    //tap.cancelsTouchesInView = false 

    view.addGestureRecognizer(tap)
}

//Calls this function when the tap is recognized.
@objc func dismissKeyboard() {
    //Causes the view (or one of its embedded text fields) to resign the first responder status.
    view.endEditing(true)
}

如果你打算在多个uiviewcontroller中使用这个功能，这里有另一种方法来完成这个任务:

// Put this piece of code anywhere you like
extension UIViewController {
    func hideKeyboardWhenTappedAround() {
        let tap = UITapGestureRecognizer(target: self, action: #selector(UIViewController.dismissKeyboard))
        tap.cancelsTouchesInView = false            
        view.addGestureRecognizer(tap)
    }
    
    @objc func dismissKeyboard() {
        view.endEditing(true)
    }
}

现在在每个UIViewController中，你要做的就是调用这个函数:

override func viewDidLoad() {
    super.viewDidLoad()
    self.hideKeyboardWhenTappedAround() 
}

这个函数是我的repo中包含的标准函数，它包含了很多有用的Swift扩展，比如这个，看看:https://github.com/goktugyil/EZSwiftExtensions

对于Swift3

在viewDidLoad中注册一个事件识别器

let tap = UITapGestureRecognizer(target: self, action: #selector(hideKeyBoard))

然后我们需要在相同的viewDidLoad中添加手势到视图中。

self.view.addGestureRecognizer(tap)

然后我们需要初始化注册的方法

func hideKeyBoard(sender: UITapGestureRecognizer? = nil){
    view.endEditing(true)
}

我没有看到它被提到过，但是NotificationCenter可以告诉你键盘何时打开和关闭。例如，如果你想改变cancelsTouchesInView或一起删除手势识别器，这可以被使用。

例子:

var dismissKeyboardGestureRecognizer = UITapGestureRecognizer()

override func viewDidLoad() {
    super.viewDidLoad()

    //Setup dismiss keyboard gesture
    self.dismissKeyboardGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(dismissKeyboard))

    //Add Notifications
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardDidShow), name:UIResponder.keyboardDidShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardDidHide), name:UIResponder.keyboardDidHideNotification, object: nil)
}

@objc func keyboardDidShow() {
    dismissKeyboardGestureRecognizer.cancelsTouchesInView = true
    view.addGestureRecognizer(dismissKeyboardGestureRecognizer)
}

@objc func keyboardDidHide() {
    dismissKeyboardGestureRecognizer.cancelsTouchesInView = false
    view.removeGestureRecognizer(dismissKeyboardGestureRecognizer)
}

@objc func dismissKeyboard() {
    view.endEditing(true)
}

我发现最好的解决方案包括来自@Esqarrouth的接受答案，并进行了一些调整:

extension UIViewController {
    func hideKeyboardWhenTappedAround() {
        let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: "dismissKeyboardView")
        tap.cancelsTouchesInView = false
        view.addGestureRecognizer(tap)
    }

    func dismissKeyboardView() {
        view.endEditing(true)
    }
}

电话响了。cancelsTouchesInView = false是关键的:它确保UITapGestureRecognizer不会阻止视图上的其他元素接收用户交互。

方法解雇键盘()被更改为稍微不那么优雅的解雇keyboardview()。这是因为在我的项目相当旧的代码库中，有很多次已经使用了dismissKeyboard()(我想这并不少见)，导致编译器问题。

然后，如上所述，这个行为可以在各个视图控制器中启用:

override func viewDidLoad() {
    super.viewDidLoad()
    self.hideKeyboardWhenTappedAround() 
}