Xcode中的Swift Playground - UILabel的TapGestureRecognizer无法正常工作

Question

我在Xcode中创建一个Swift Playground，我将TapGestureRecognizer放到UILabel上有问题...

class MyViewController : UIViewController {

  override func loadView() {

    func tapped() {

        print("The label was tapped!")

    }

    let label11 = UILabel()
    label11.frame = CGRect(x: -350, y: 360, width: 350, height: 20)
    label11.text = "name."
    label11.textColor = .black
    label11.isUserInteractionEnabled = true
    view.addSubview(label11)

    let tap = UITapGestureRecognizer(target: self, action: "tapped")
    label11.addGestureRecognizer(tap)
  }
}

Answer 1

您似乎是以编程方式创建视图控制器，因为您只在loadView中操作（您正确地没有调用super），这需要您创建该控制器的实际view。

import UIKit
import PlaygroundSupport

class MyViewController: UIViewController {

    override func loadView() {

        view = UIView()

        let label11 = UILabel()
        label11.frame = CGRect(x: 0, y: 360, width: 350, height: 20)
        label11.text = "name."
        label11.textColor = .yellow
        label11.isUserInteractionEnabled = true
        view.addSubview(label11)

        let tap = UITapGestureRecognizer(target: self, action: #selector(tapped))
        label11.addGestureRecognizer(tap)

    }

    @objc func tapped() {
        print("The label was tapped!")
    }

}

PlaygroundPage.current.liveView = MyViewController()

或者，您可以使用viewDidLoad（需要您调用super）来复制非编程视图控制器。

import UIKit
import PlaygroundSupport

class MyViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let label11 = UILabel()
        label11.frame = CGRect(x: 0, y: 360, width: 350, height: 20)
        label11.text = "name."
        label11.textColor = .yellow
        label11.isUserInteractionEnabled = true
        view.addSubview(label11)

        let tap = UITapGestureRecognizer(target: self, action: #selector(tapped))
        label11.addGestureRecognizer(tap)

    }

    @objc func tapped() {
        print("The label was tapped!")
    }

}

PlaygroundPage.current.liveView = MyViewController()

此外，您的origin-x值超出界限，这就是为什么您可能没有看到标签，并且您缺少Swift 4中所需的@objc语法。