子视图在xcode游乐场中不工作

你做了很多错事:(

这将在操场页面上运行,并且应该接近您想要的内容。查看评论以了解情况:

import UIKit
import Foundation
import PlaygroundSupport

class SecondView : UIView{

    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }

    public required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }

    func commonInit() {

        // create a label
        let label = UILabel()
        // we're going to use auto-layout
        label.translatesAutoresizingMaskIntoConstraints = false

        // add the label to self
        self.addSubview(label)

        // pin the label to leading, trailing and bottom -- all to Zero
        label.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 0.0).isActive = true
        label.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: 0.0).isActive = true
        label.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: 0.0).isActive = true

        label.textAlignment = .center
        label.font = UIFont(name: "helveticaneue-ultraLight", size: 40)
        label.text = "Hejsan"
        label.textColor = .white

    }

}

class MyViewController : UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        // we don't need to create a new view
        //let view = UIView()

        view.backgroundColor = .green

        // create the "SecondView"
        let sView = SecondView()
        // we're going to use auto-layout
        sView.translatesAutoresizingMaskIntoConstraints = false

        // add the new view
        view.addSubview(sView)

        // pin the new view to top, leading and trailing -- all to Zero so it fills this view
        sView.topAnchor.constraint(equalTo: view.topAnchor, constant: 0.0).isActive = true
        sView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0.0).isActive = true
        sView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0.0).isActive = true
        sView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 0.0).isActive = true

        sView.backgroundColor = .red

    }

}

// Present the view controller in the Live View window

let vc = MyViewController()
vc.preferredContentSize = CGSize(width: 375, height: 667)
PlaygroundPage.current.liveView = vc

结果:

声明子视图的正确方法

class SecondView: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)
        sharedLayout()

    }

    required init(coder aDecoder: NSCoder) {
        super.init(coder : aDecoder)
        sharedLayout()
    }

    func sharedLayout()
    {
         let label = UILabel()
         label.frame = CGRect(x: 0, y: 335, width: 400, height: 53)
         label.textAlignment = .center
         label.font = UIFont(name: "helveticaneue-ultraLight", size: 40)
         label.text = "Hejsan"
         label.textColor = .white
         self.addSubview(label)
         print("Test")
    }

}

loadView 是一个 UIViewController 生命周期回调方法(请参阅 docs )。

你的 SecondView 是的子类 UIView 这没有定义 加载视图 。因此 加载视图 您在中实现 第二视图 不会被环境调用。您必须明确地调用它:

let sView = SecondView()
sView.backgroundColor = .red
sView.frame = view.frame

sView.loadView()

view.addSubview(sView)

此外,我建议将其重命名(以便与 UIViewController 的 加载视图 。

更新

还有其他几个错误。

1. :在您的 加载视图 您正在创建的第二个视图的 第二视图 并将标签添加到其中。您需要将其添加到 self 。

2. :英寸 加载视图 在viewController的 view 具有 UIView() 默认为 UIView(frame: CGRect.zero) 然后你设置 sView.frame = view.frame 这将构成第二个视图的框架 CGRect.zero 也 看法 将由 UIViewController 环境,但 sView 不会更新。有几种方法可供选择,但最简单的方法是初始化 看法 使用适当的 frame 从一开始。工作场所解决方案:

import UIKit
import Foundation
import PlaygroundSupport

class SecondView : UIView{

    func loadView() {
        let label = UILabel()
        label.frame = CGRect(x: 0, y: 335, width: 400, height: 53)

        label.textAlignment = .center
        label.font = UIFont(name: "helveticaneue-ultraLight", size: 40)
        label.text = "Hejsan"
        label.textColor = .white

        self.addSubview(label)
        print("Test")
    }

}

class MyViewController : UIViewController {

    //Outlets
    let profileButton = UIButton()

    override func loadView() {
        let view = UIView(frame: UIScreen.main.bounds)

        view.backgroundColor = .green
        print(view.frame)

        let sView = SecondView()
        sView.backgroundColor = .red
        sView.frame = view.frame
        sView.loadView()

        view.addSubview(sView)

        print(sView.frame)

        self.view = view

    }
}
// Present the view controller in the Live View window

PlaygroundPage.current.liveView = MyViewController()