How to add a subview with constraints to make the subview with the same frame as its superview?

2
votes

Within UIView I have a method presentView(): 

public func presentView() {

    UIApplication.sharedApplication().delegate?.window??.addSubview(self)

    let blurEffect = UIBlurEffect(style: .Light)
    let blurEffectView = UIVisualEffectView(effect: blurEffect)
    blurEffectView.backgroundColor = UIColor.yellowColor()
    addSubview(blurEffectView)

    let topConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Top, relatedBy: .Equal, toItem: self, attribute: .Bottom, multiplier: 1, constant: 0)
    let bottomConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Bottom, relatedBy: .Equal, toItem: self, attribute: .Top, multiplier: 1, constant: 0)
    let leadingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Leading, relatedBy: .Equal, toItem: self, attribute: NSLayoutAttribute.Leading, multiplier: 1, constant: 0)
    let trailingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Trailing, relatedBy: .Equal, toItem: self, attribute: NSLayoutAttribute.Trailing, multiplier: 1, constant: 0)

    self.addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint])

    print("newframe: \(blurEffectView.frame)")

}

but sth is wrong because this is the output on console:

newframe: (0.0, 0.0, 0.0, 0.0)

and result is:

enter image description here

1
iosswiftuiviewnslayoutconstraint
If I'm reading correctly, self is a UIView. Then you should add the constraints to self rather then blurEffectView. – Dániel Nagy
@DánielNagy I updated the question, can you help me to solve this out? – Bartłomiej Semańczyk
I think until the view is not layed out, you won't get it's actual frame. So after self.addConstraints you won't get it right now. – Dániel Nagy
Again updated the question with new info. I set background color to yellow, but there is no my view at all. – Bartłomiej Semańczyk
This SO question has a lot of good information on programmatically adding constraints. – Derek Soike

1 Answers

13
votes

Remember about:

blurEffectView.translatesAutoresizingMaskIntoConstraints = false

and then:

let topConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Top, relatedBy: .Equal, toItem: self, attribute: .Top, multiplier: 1, constant: 0)
let bottomConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Bottom, relatedBy: .Equal, toItem: self, attribute: .Bottom, multiplier: 1, constant: 0)
let leadingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Leading, relatedBy: .Equal, toItem: self, attribute: .Leading, multiplier: 1, constant: 0)
let trailingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Trailing, relatedBy: .Equal, toItem: self, attribute: .Trailing, multiplier: 1, constant: 0)

addSubview(blurEffectView)
addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint])
layoutIfNeeded()