Custom View - self.frame is not correct?

Question

So I have a custom UIView class

class MessageBox: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        createSubViews()
    }
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        createSubViews()
    }
    func createSubViews() {

        let testView = UIView(frame: self.frame)
        testView.backgroundColor = UIColor.brown
        self.addSubview(testView)
    }
}

I added a UIView inside the storyboard and gave it some constraints:

100 from the top (superview), 0 from the left and right, height is 180

But when I run the app the brown subview I created in the code is way to big. I printed self.frame in my custom view and it turns out that the frame is (0,0,1000,1000). But why? I set constraints, it should be something like (0,0,deviceWith, 180).

What did I do wrong?

EDIT: That's my Storyboard setup:

Solution 1

Short and simple answer:

You're doing it too early.

---

Detailed answer:

When a view is initialized from an Interface Builder file (a xib or a storyboard) its frame is initially set to the frame it has in Interface Builder. You can look at it as a temporary placeholder.

When using Auto Layout the constraints are resolved (= the view's actual frame is computed) inside the view's layoutSubviews() method.

Thus, there are two possible solutions for your problem:

1. (preferrable) If you use Auto Layout, use it throughout your view.

   • Either add your testView in Interface Builder as well and create an outlet for it
   • or create your testView in code as you do, then set its translatesAutoResizingMaskIntoConstraints property to false (to sort of "activate Auto Layout") and add the required constraints for it in code.

2. Set your testView's frame after the MessageBox view's frame itself has been set by the layout engine. The only place where you can be sure that the system has resolved the view's frame from the constraints is when layoutSubviews() is called.

   override func layoutSubviews() {
       super.layoutSubviews()
       testView.frame = self.frame
   }
   

   (You need to declare your testView as a property / global variable, of course.)

Solution 2

Try to use the anchors for your view:

MessageBox.centerXAnchor.constraintEqualToAnchor(self.view.centerXAnchor).active
= true 
MessageBox.centerYAnchor.constraintEqualToAnchor(self.view.centerYAnchor).active
= true 
MessageBox.widthAnchor.constraintEqualToConstant(150).active = true 
MessageBox.heightAnchor.constraintEqualToConstant(100).active = true

This method have to be used inside your class

Solution 3

override func layoutSubviews() {
    super.layoutSubviews()
    testView.frame = self.frame
}

this also works when you add a custom class to a UIView in the storyboard and that uses autolayout. thanks Mischa !

Comments

[Quantm]

tried it, but the problem is that the superview's height and width is 1000. But I don't know why

[Dasem]

probabley because , the layout engine has not finished it’s job yet, so you can’t rely on the frame and bounds size in the method

[Quantm]

The problem is that I can't, for instance, transform the testView as layoutSubviews() would reset it immediately after that. I think the problem is that inside the init?(coder aDecoder: NSCoder) method the frame hasen't been calculated yet, thus I can't use it. I somehow have to bypass that, I think

[Quantm]

I just posted a similar question regarding that as this could be a bit off-topic here. I will post a complete answer here if I have one. Or maybe someone else has an idea :)

[Abhishek]

Thanks for your answer but if we need to pass some data to Custom UIView which needs to used inside layoutSubviews, how can we do this ?