ios 坚持以编程方式在 swift 3 中向按钮添加目标

Stuck with adding target to button in swift 3 programmatically

提问by user234159

I've created a UIButton using Swift 3 and I want it to print some message when it's pressed.

我已经使用 Swift 3 创建了一个 UIButton，我希望它在按下时打印一些消息。

So I did something like this: In loadView()

所以我做了这样的事情：在 loadView()

button.addTarget(self, action: #selector(ViewController.pressButton(button:)), for: .touchUpInside)

A method:

一个方法：

func pressButton(button: UIButton) {

    NSLog("pressed!")

}

But nothing happens when I click the button.

但是当我点击按钮时没有任何反应。

回答by Rashwan L

Add the button code in your viewDidLoadand it will work for you:

在您的按钮中添加按钮代码，viewDidLoad它将为您工作：

override func viewDidLoad() {
    super.viewDidLoad()
    let button = UIButton(frame: CGRect(x: 10, y: 10, width: 100, height: 100))
    button.backgroundColor = UIColor.gray
    button.addTarget(self, action: #selector(pressButton(button:)), for: .touchUpInside)
    self.view.addSubview(button)
}

func pressButton(button: UIButton) {
    NSLog("pressed!")
}

You don′t need to add ViewController.pressButtonto selector, it′s enough with the function name.

你不需要添加ViewController.pressButton到selector，它就足够了function name。

Swift 4.x version:

斯威夫特 4.x 版本：

let button = UIButton(frame: CGRect(x: 10, y: 10, width: 100, height: 100))
button.backgroundColor = .gray
button.tag = 0
button.addTarget(self, action: #selector(pressButton(_:)), for: .touchUpInside)
self.view.addSubview(button)

@objc func pressButton(_ button: UIButton) {
    print("Button with tag: \(button.tag) clicked!")
}

Swift 5.1 version:

斯威夫特 5.1 版本：

let button = UIButton(frame: CGRect(x: 10, y: 10, width: 100, height: 100))
button.backgroundColor = .gray
button.tag = 100
button.addTarget(self, action: #selector(pressButton), for: .touchUpInside)
self.view.addSubview(button)

@objc func pressButton(button: UIButton) {
    print("Button with tag: \(button.tag) clicked!")
}

回答by Otis Lee

try this in Swift3!

在 Swift3 中试试这个！

button.addTarget(self, action: #selector(self.pressButton(button:)), for: .touchUpInside)

@objc func pressButton(button: UIButton) { NSLog("pressed!") }

回答by arango_86

Use the following code.

使用以下代码。

button.addTarget(self, action: #selector(FirstViewController.cartButtonHandler), for: .touchUpInside)

Your class name corresponds to FirstViewController

你的类名对应于FirstViewController

And your selector corresponds to the following function

并且您的选择器对应于以下功能

func cartButtonHandler() {

}

回答by Nikhil Manapure

In swift 3 use this -

在 swift 3 中使用这个 -

object?.addTarget(objectWhichHasMethod, action: #selector(classWhichHasMethod.yourMethod), for: someUIControlEvents)

For example(from my code) -

例如（来自我的代码）-

self.datePicker?.addTarget(self, action:#selector(InfoTableViewCell.datePickerValueChanged), for: .valueChanged)

Just give a :after method name if you want the sender as parameter.

:如果您希望发件人作为参数，只需在方法名称之后给出。

回答by BHendricks

You mention that the addTargetcall is in loadView(). Is this in your custom subview, of some kind, or the viewController?

您提到addTarget呼叫在loadView(). 这是在您的自定义子视图中，某种类型，还是视图控制器？

From your selector, it's targeting a method in your ViewControllerclass, but if the targetfor this action is the view itself, then it would make sense that the action is not going through.

从您的选择器来看，它的目标是您的ViewController类中的一个方法，但是如果target此操作是视图本身，那么该操作没有通过就有意义了。

If you declare your button in a viewController, and in viewDidLoadadd this target as above, then the message should be printed as you're looking for. I believe you are "targetting" the wrong class with your action.

如果您在 viewController 中声明您的按钮，并按viewDidLoad上述方式添加此目标，则应按您的要求打印消息。我相信您的行动“瞄准”了错误的班级。

回答by Divya Rayapati

 let cancelButton = UIButton.init(frame: CGRect(x: popUpView.frame.size.width/2, y: popUpView.frame.size.height-20, width: 30, height: 30))
        cancelButton.backgroundColor = UIColor.init(patternImage: UIImage(named: cancelImage)!)
        cancelButton.addTarget(self, action: #selector(CommentsViewController.canceled), for:.touchUpInside)

回答by SpkingR

1. Add the button code in override func viewDidLoad()method

2. Make sure your action handler tagged with @IBAction like this:

   @IBAction func pressButton(button: UIButton) { print("pressed!") }

1. 在override func viewDidLoad()方法中添加按钮代码

2. 确保你的动作处理程序像这样用@IBAction 标记：

   @IBAction func pressButton(button: UIButton) { print("pressed!") }

Then it will work!

然后它会起作用！