Swift: Background gradient for UIView

Question

I'm having trouble trying to add a gradient background to UIView. I made an extension of UIView and added the following method:

func setGradientBackground(colorTop: UIColor, colorBottom: UIColor) {
    let gradientLayer = CAGradientLayer()
    gradientLayer.colors = [colorTop, colorBottom]
    gradientLayer.frame = bounds

    layer.insertSublayer(gradientLayer, at: 0)
}

Then I call:

separatorView.setGradientBackground(colorTop: .clear, colorBottom: .red)

But it doesn't work. The view is presented but its background is entirely clear. I tried as well with CGColor

Answer 1

There were 2 problems:

• I needed to set the start and end points to provide a gradient direction:

  func setGradientBackground(colorTop: UIColor, colorBottom: UIColor) {
      let gradientLayer = CAGradientLayer()
      gradientLayer.colors = [colorBottom.cgColor, colorTop.cgColor]
      gradientLayer.startPoint = CGPoint(x: 0.5, y: 1.0)
      gradientLayer.endPoint = CGPoint(x: 0.5, y: 0.0)
      gradientLayer.locations = [0, 1]
      gradientLayer.frame = bounds
  
     layer.insertSublayer(gradientLayer, at: 0)
  }
  

• And the second issue was that CAGradientLayer takes effect after the view is layed out. I solved that calling setGradientBackground() on viewDidAppear:

  override func viewDidAppear(_ animated: Bool) {
      super.viewDidAppear(animated)
      separatorView.setGradientBackground(colorTop: .clear, colorBottom: Colors.darkGrey)
  }