override func viewDidLoad() {
    super.viewDidLoad()

    self.blurView = UIVisualEffectView(effect: UIBlurEffect(style: .ExtraLight)) as UIVisualEffectView
    self.view.insertSubview(self.blurView,belowSubview: self.filterPanel)

    self.blurView.addConstraint(NSLayoutConstraint(item: self.blurView,attribute: NSLayoutAttribute.Top,relatedBy: NSLayoutRelation.Equal,toItem: self.view,multiplier: 1,constant: 0))
    self.blurView.addConstraint(NSLayoutConstraint(item: self.blurView,attribute: NSLayoutAttribute.Bottom,attribute: NSLayoutAttribute.Leading,attribute: NSLayoutAttribute.Trailing,constant: 0))
}

当调用上面的代码时,它崩溃并出现错误“视图层次结构没有为约束做好准备”.我可以理解,如果我在尝试在将约束添加到视图之前添加约束但是插入了视图,然后添加了约束,则会生成此错误.

有任何想法吗？