迅速的游乐场显示不间断循环的uiview

Question

我在实时视图窗口中创建并显示uiview，当我创建按钮并将其添加到uiview时，程序会因不间断循环而失败，并不断加载addbutton。有人遇到这个问题了吗，请告诉我原因：-）

import UIKit
import PlaygroundSupport

class MyViewController : UIViewController {

var label1 : UILabel?

override func loadView() {
    let view = UIView()
    view.backgroundColor = .white

    print("code run here ")

    let label = UILabel()
    label.frame = CGRect(x: 150, y: 200, width: 200, height: 20)
    label.text = "Hello World!"
    label.textColor = .black

    label1 = label
    view.addSubview(label)

    let  k1:UIButton = addnewbutton() as! UIButton
    //view.addSubview(k1)

    self.view = view
}

@objc func buttonPressed(sender: UIButton!) {
    var alertController = UIAlertController(title: "title", message: "message", preferredStyle: UIAlertControllerStyle.alert)
   self.present(alertController, animated: true, completion: nil)
}

func addnewbutton() -> UIView{
    var btn : UIButton
    btn = UIButton()
    btn.frame  = CGRect(x:200,y:300,width:100,height:25)
    btn.setTitle("clickme",for: UIControlState.normal)
    //btn.titleLabel?.text = "clickme"
    btn.backgroundColor = UIColor.black
    btn.titleLabel?.textColor = UIColor.white
    btn.titleColor(for: UIControlState.normal)
    btn.addTarget(self, action: #selector(buttonPressed), for: UIControlEvents.touchUpInside)
    view.addSubview(btn)

    return btn
    }
}

// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()

Answer 1

您在此处添加按钮

fetch

在view.addSubview(btn) 内

它以递归方式搜索VC的父视图，并且尚未在addnewbutton中设置它，因此控件再次调用它，问题就发生了无限循环，因此请注释该行并取消注释

loadView

顺便说一句，view.addSubview(k1) // which is inside loadView 直接返回addnewbutton，而不是强制转换