Ios 无法正确定位UIActivityIndicator视图

我在场景中添加了UIActivityIndicatorView，效果很好。然后我尝试添加一个小容器，并在上面显示活动指示器

这是我的密码

func showActivityIndicator(uiView: UIView) {
    let container: UIView = UIView()
    container.frame = CGRect(x: 0.0, y: 0.0, width: 80.0, height: 80.0);
    container.center = uiView.center
    container.backgroundColor = UIColor(red: 0.0, green: 0.0, blue: 0.0, alpha: 0.5)

    let activityIndicator = UIActivityIndicatorView()
    activityIndicator.frame = CGRect(x: 0.0, y: 0.0, width: 40.0, height: 40.0);
    activityIndicator.center = uiView.center
    activityIndicator.hidesWhenStopped = true
    activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.gray

    container.addSubview(activityIndicator)
    uiView.addSubview(container)

    activityIndicator.startAnimating()
}

容器视图显示在屏幕中间，但没有活动指示器。当我检查debug视图层次结构时，我看到活动指示器位于视图的右下角。有人能解释一下为什么在我添加容器后它会出现在那里吗？我如何才能正确定位它

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谢谢。

以下代码有问题

 activityIndicator.center = uiView.center

请试试这个

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

这将有助于：

func showActivityIndicator(uiView: UIView) {
      let container: UIView = UIView()
      container.frame = CGRect(x: 0.0, y: 0.0, width: 80.0, height: 80.0);
      container.center = uiView.center
      container.backgroundColor = UIColor(red: 0.0, green: 0.0, blue: 0.0, alpha: 0.5)

      let activityIndicator = UIActivityIndicatorView()
      activityIndicator.center = container.center
      activityIndicator.hidesWhenStopped = true
      activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.gray

     container.addSubview(activityIndicator)
     uiView.addSubview(container)

     activityIndicator.startAnimating()
}

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不，这不起作用。在函数“container.center=uiView.center”的第3行中。