实现从SwiftUI到UIView的填充

好的，最简单的是基于corse Storyboard的方法(如@sagar_chauhan所示).

下面是提供的逐行游乐场变体(例如，按代码行与SwiftUI预览进行比较)。

import UIKit
import PlaygroundSupport

class MyViewController : UIViewController {
    override func loadView() {
        let view = UIView(frame: CGRect(x: 0, y: 0, width: 375, height: 677))
        view.translatesAutoresizingMaskIntoConstraints = false
        view.backgroundColor = .white

        self.view = view
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        let label = UILabel(frame: .zero)
        label.translatesAutoresizingMaskIntoConstraints = false
        label.text = "Hello World!"
        label.textColor = .black
        label.backgroundColor = .yellow
        label.textAlignment = .center

        self.view.addSubview(label)

        let fitSize = label.sizeThatFits(view.bounds.size)
        label.widthAnchor.constraint(equalToConstant: fitSize.width + 12.0).isActive = true
        label.heightAnchor.constraint(equalToConstant: fitSize.height + 12.0).isActive = true


        label.topAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true
        label.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
    }
}

PlaygroundPage.current.liveView = MyViewController()