在Swift中在现有图层下插入子图层时出现问题？

Question

我正在尝试在Swift中添加一个现有图层后面的子图层，但子图层仍然在现有图层前面 - 我的代码中必须有问题;

import UIKit

class ViewController: UIViewController {

let mainView = UIView()
let screenWidth = UIScreen.main.bounds.width
let screenHeight = UIScreen.main.bounds.height
let focusBG = UIView()

override func viewDidLoad() {
    super.viewDidLoad()

    mainView.backgroundColor = UIColor.gray
    view.addSubview(mainView)
    mainView.translatesAutoresizingMaskIntoConstraints = false
    mainView.widthAnchor.constraint(equalToConstant: 325).isActive = true
    mainView.heightAnchor.constraint(equalToConstant: ((325 / 9) * 16)).isActive = true
    mainView.topAnchor.constraint(equalTo: view.topAnchor, constant: 100).isActive = true
    mainView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true

    let tapView = UIView(frame: CGRect(x: 50, y: 0, width: 150, height: 200))
    tapView.backgroundColor = UIColor.red
    mainView.addSubview(tapView)

    focusBG.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
    focusBG.backgroundColor = UIColor(hue: 0.0, saturation: 0.0, brightness: 0.0, alpha: 0.4)
    self.view.layer.insertSublayer(focusBG.layer, below: tapView.layer)
}

}

理想情况下，红色框将位于灰色图层的前面 - 但这正是我得到的;

谢谢！

更新：工作准则

        self.mainView.insertSubview(focusBG, belowSubview: tapView)

    focusBG.translatesAutoresizingMaskIntoConstraints = false
    focusBG.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
    focusBG.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
    focusBG.widthAnchor.constraint(equalToConstant: screenWidth).isActive = true
    focusBG.heightAnchor.constraint(equalToConstant: screenHeight).isActive = true

Answer 1

你可以试试

self.mainView.insertSubview(focusBG, belowSubiew: tapView)

要么

self.mainView.layer.insertSublayer(focusBG.layer, below: tapView.layer) // not tested 

Answer 2

尝试使用insertSublayer，方法适合我。

self.mainView.layer.insertSublayer(your_Layer, at: 1) // 1 is the position of the layer you want to add to the mainView.

谢谢，让我知道这是否适合你。如果确实如此，请不要忘记投票;）