Multiple shadows under UIView iOS Swift - ios

Question

I am trying to make a UIButton with rounded corners that has 2 colored shadows. Why is the red (and at this point also the blue "shadow" layer covering the button? How to get the shadows below the button canvas). I thought it was helping to insert sublayers instead of just adding them.
I have made a playground illustrating the issue
import UIKit
import PlaygroundSupport
This is the button I'm trying to implement
class PrimaryButton: UIButton {
required init(text: String = "Test 1", hasShadow: Bool = true) {
super.init(frame: .zero)
setTitle(text, for: .normal)
backgroundColor = UIColor.blue
layer.cornerRadius = 48 / 2
layer.masksToBounds = false
if hasShadow {
insertShadow()
}
}
fileprivate func insertShadow() {
let layer2 = CALayer(layer: layer), layer3 = CALayer(layer: layer)
layer2.applySketchShadow(color: UIColor.red, alpha: 0.5, x: 0, y: 15, blur: 35, spread: -10)
layer3.applySketchShadow(color: UIColor.blue, alpha: 0.5, x: 0, y: 10, blur: 21, spread: -9)
layer.insertSublayer(layer2, at: 0)
layer.insertSublayer(layer3, at: 0)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func layoutSubviews() {
super.layoutSubviews()
layer.sublayers?.forEach { (sublayer) in
sublayer.shadowPath = UIBezierPath(rect: bounds).cgPath
}
}
}
This is an extension that helps adding the shadow from Sketch specification:
extension CALayer {
func applySketchShadow(
color: UIColor = .black,
alpha: Float = 0.5,
x: CGFloat = 0,
y: CGFloat = 2,
blur: CGFloat = 4,
spread: CGFloat = 0)
{
shadowColor = color.cgColor
shadowOpacity = alpha
shadowOffset = CGSize(width: x, height: y)
shadowRadius = blur / 2.0
if spread == 0 {
shadowPath = nil
} else {
let dx = -spread
let rect = bounds.insetBy(dx: dx, dy: dx)
shadowPath = UIBezierPath(rect: rect).cgPath
}
masksToBounds = false
}
}
class MyViewController : UIViewController {
override func loadView() {
let view = UIView()
view.backgroundColor = .white
let button = PrimaryButton()
button.frame = CGRect(x: 150, y: 200, width: 200, height: 48)
view.addSubview(button)
self.view = view
}
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()

Answer 1

It seems legit to me. layer1 & layer2 are sublayers of the button layer.
You could add a third layer that will serve as a background. Here is an example based on your code:
class PrimaryButton: UIButton {
let layer1 = CALayer(), layer2 = CALayer(), layer3 = CALayer()
override func layoutSubviews() {
super.layoutSubviews()
layer1.backgroundColor = UIColor.blue.cgColor
layer1.cornerRadius = 48 / 2
[layer1, layer2, layer3].forEach {
$0.masksToBounds = false
$0.frame = layer.bounds
layer.insertSublayer($0, at: 0)
}
layer2.applySketchShadow(color: UIColor.red, alpha: 0.5, x: 0, y: 15, blur: 35, spread: -10)
layer3.applySketchShadow(color: UIColor.blue, alpha: 0.5, x: 0, y: 10, blur: 21, spread: -9)
}
}
Note that I put most of the code inside layoutSubviews because most of your methods use the actual bounds of the button.

Answer 2

Change your insertions to:
layer.insertSublayer(layer2, at: 1)
layer.insertSublayer(layer3, at: 2)
That should do it.

Answer 3

Another way is to add double buttons without change your class.
let button = PrimaryButton()
button.frame = CGRect(x: 150, y: 200, width: 200, height: 48)
button.backgroundColor = UIColor.clear
view.addSubview(button)
self.view = view
let button1 = PrimaryButton()
button1.frame = CGRect(x: 0, y: 0, width: 200, height: 48)
button.addSubview(button1)
button1.layer.sublayers?.forEach{$0.removeFromSuperlayer()}