SubView of SceneView并非总是居中

Question

当将CoachingOverlay添加到SceneView (在viewDidLoad中)时，覆盖有时不是居中的，而是出现在屏幕的右下角。这一切为什么要发生？如果屏幕有双倍大小，则右下角的覆盖将居中，那么大小还没有设置吗？或者可能是因为我在自定义的反应本机模块中使用ARKit？谢谢

coachingOverlay.translatesAutoresizingMaskIntoConstraints = false
sceneView.addSubview(coachingOverlay)
NSLayoutConstraint.activate([
  coachingOverlay.centerXAnchor.constraint(equalTo: sceneView.centerXAnchor),
  coachingOverlay.centerYAnchor.constraint(equalTo: sceneView.centerYAnchor),
  coachingOverlay.widthAnchor.constraint(equalTo: sceneView.widthAnchor),
  coachingOverlay.heightAnchor.constraint(equalTo: sceneView.heightAnchor)
])`

同样的事情发生在一个MBProgressHUD上：

self.hud = MBProgressHUD.showAdded(to: self.sceneView, animated: true)   

Answer 1

我通过在视图/sceneview和hud和coachingoverlay子视图之间添加一个额外的视图来解决这个问题：

let container = UIView(frame: UIScreen.main.bounds)
self.view.addSubview(container)
self.hud = MBProgressHUD.showAdded(to: container, animated: true)
NSLayoutConstraint.activate([
  self.hud.centerXAnchor.constraint(equalTo: container.centerXAnchor),
  self.hud.centerYAnchor.constraint(equalTo: container.centerYAnchor),
  self.hud.widthAnchor.constraint(equalTo: container.widthAnchor),
  self.hud.heightAnchor.constraint(equalTo: container.heightAnchor)
])

Answer 2

请尝尝这个

yourSubView.center = CGPoint(x: yourView.frame.size.width  / 2,
                         y: yourView.frame.size.height / 2)