Programmatically created shadow doesn't display - ios

Question

I have iOS app where I have a couple views with a shadow (Called them shadowView for convenience). This is how they're made:
let shadowView = UIView(frame: .zero)
self.addSubview(shadowView)
shadowView.layer.shadowColor = UIColor.black.cgColor
shadowView.layer.shadowOffset = CGSize(width: 0.5, height: 1.5)
shadowView.layer.shadowOpacity = 0.15
shadowView.layer.masksToBounds = false
shadowView.layer.cornerRadius = 8
shadowView.backgroundColor = .clear
shadowView.layer.shadowRadius = 5.0
shadowView.clipsToBounds = false
shadowView.layer.shadowPath = UIBezierPath(roundedRect: shadowView.bounds, cornerRadius: 20).cgPath
The view is then placed in position with Snapkit, but I left out that part of the code due to it being irrelevant. Now the shadow that I made here is not displayed. However, if I set the backgroundColor property to e.g. UIColor.yellow then the view itself shows, but not the shadow.
I also checked if the shadow might be cut off by any parent view, which doesn't seem to be the case.
As you can see it's not the usual clipsToBounds / masksToBounds mistake, and I've been looking at this for the last couple hours. Am I missing a piece of code maybe? Or did I miss anything?

Answer 1

Your frame size is .zero. Assign some valid size to it.

Answer 2

Give the view a non-zero frame size
let viewWidth = //any
let viewHeight = //any
let shadowView = UIView(frame: CGRect.init(x: 0, y: 0, width: viewWidth, height: viewHeight))

Answer 3

To try and clarify...
You are setting .shadowPath, but based on you code you're setting it prior to .shadowView having its frame set. So, you are creating a UIBezierPath with a frame of .zero -- and it never changes.
You need to set the shadow path either in viewDidLayoutSubviews of a view controller, or by overriding layoutSubviews() inside your custom view.
Here is a simple example that you can run in a Playground page:
import UIKit
import PlaygroundSupport
class TestViewController : UIViewController {
let shadowView = UIView(frame: .zero)
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(shadowView)
shadowView.layer.shadowColor = UIColor.black.cgColor
shadowView.layer.shadowOpacity = 0.15
shadowView.layer.cornerRadius = 8
shadowView.backgroundColor = .clear
// this would be handled by your use of SnapKit
shadowView.translatesAutoresizingMaskIntoConstraints = false
shadowView.topAnchor.constraint(equalTo: view.topAnchor, constant: 40.0).isActive = true
shadowView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20.0).isActive = true
shadowView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20.0).isActive = true
shadowView.heightAnchor.constraint(equalToConstant: 100).isActive = true
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
shadowView.layer.shadowPath = UIBezierPath(roundedRect: shadowView.bounds, cornerRadius: 20).cgPath
}
}
let vc = TestViewController()
vc.view.backgroundColor = .white
PlaygroundPage.current.liveView = vc

Answer 4

Like other colleagues said, the frame of your view is the problem.
This is a problem just because you set the layer's shadow path to be as big as the view's bounds that in that moment is .zero.
Still I understand that you want your view to react to its constraint when the auto-layout engine is ready to layout your views. There are then two things you can do to address this problem:
1) you can remove the explicit set of shadowView.layer.shadowPath and change the color of the view from clear to another color. This will cause the shadow to follow the shape of the view even if it changes, with a dynamic shadow path. While this will fix the issue, sometimes it results also in an impact on performance during animations and transitions.
2) if the view doesn't change its size during her life on screen you can force the superView to re-layout itself right after you add the shadowView as subview.
self.addSubview(shadowView)
self.setNeedsLayout()
self.layoutIfNeeded()
In this way when you'll create the shadow path bounds will not be zero because auto layout already did its magic changing the frame of your view.
Please note that with the second solution you will not see the view (that has clear color) but just its shadow.

Answer 5

Swift 4
Add this function in your view controller
func addShadow(myView: UIView?) {
myView?.layer.shadowColor = UIColor.black.cgColor
myView?.layer.shadowOffset = CGSize(width: 0, height:0)
myView?.layer.shadowOpacity = 0.3
myView?.layer.shadowRadius = 5
myView?.layer.masksToBounds = false
myView?.layer.cornerRadius = 12
}
and use it like:
let shadowView = UIView(frame: CGRect(x: 0, y: 0, width: yourWidth, height: yourHeight))
self.addShadow(shadowView)