Swift - 约束或其锚点引用不同视图层次结构中的项

Question

I am getting this error message:

'Unable to activate constraint with anchors and because they have no common ancestor. Does the constraint or its anchors reference items in different view hierarchies? That's illegal.'

I basically know what the problem is but I have no idea how to fix it. I am trying to dismiss views like this:

func dismissPopUpView(){
    UIView.animate(withDuration: 0.3, animations: {
        self.popUpView.transform =  CGAffineTransform(scaleX: 1.3, y: 1.3)
        self.wishButton.alpha = 0
        self.popUpView.alpha = 0
        self.visualEffectView.alpha = 0
        self.dropDownButton.alpha = 0
        self.closeButton.alpha = 0
    }) { (_) in
        self.dropDownButton.dismissDropDown()
        self.dropDownButton.dropView.removeFromSuperview()
        self.dropDownButton.removeFromSuperview()
        self.wishButton.removeFromSuperview()
        self.visualEffectView.removeFromSuperview()
        self.closeButton.removeFromSuperview()
        self.popUpView.removeFromSuperview()
    }
}

The problem is that dropDownButton.dropView is created within the dropDownButton - class like this:

override func didMoveToSuperview() {
    self.superview?.addSubview(dropView)
    self.superview?.bringSubviewToFront(dropView)
    dropView.topAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
    dropView.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
    dropView.widthAnchor.constraint(equalTo: self.widthAnchor).isActive = true
    height = dropView.heightAnchor.constraint(equalToConstant: 0)
}

var isOpen = false

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    if isOpen == false {

        isOpen = true

        NSLayoutConstraint.deactivate([self.height])

        if self.dropView.tableView.contentSize.height > 150 {
            self.height.constant = 150
        } else {
            self.height.constant = self.dropView.tableView.contentSize.height
        }


        NSLayoutConstraint.activate([self.height])

        UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.5, initialSpringVelocity: 0.5, options: .curveEaseInOut, animations: {
            self.dropView.layoutIfNeeded()
            self.dropView.center.y += self.dropView.frame.height / 2
        }, completion: nil)

    } else {
        isOpen = false

        NSLayoutConstraint.deactivate([self.height])
        self.height.constant = 0
        NSLayoutConstraint.activate([self.height])
        UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.5, initialSpringVelocity: 0.5, options: .curveEaseInOut, animations: {
            self.dropView.center.y -= self.dropView.frame.height / 2
            self.dropView.layoutIfNeeded()
        }, completion: nil)

    }
}

I thought dismissing the dropView first and then dropDownButton will solve the problem but it doesn't. Anyone know how I can fix this?

Answer 1

I finally got it working. I added this inside my dropDownBtn - class :

override func removeFromSuperview() {
    dropView.bottomAnchor.constraint(equalTo: self.topAnchor).isActive = false
    dropView.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = false
    dropView.widthAnchor.constraint(equalTo: self.widthAnchor).isActive = false
}