# CAGradientLayer

# Creating a CAGradientLayer

// View to hold the CAGradientLayer.
let view: UIView = UIView(frame: CGRect(x: 0, y: 0, width: 320, height: 320))
    
// Initialize gradient layer.
let gradientLayer: CAGradientLayer = CAGradientLayer()
    
// Set frame of gradient layer.
gradientLayer.frame = view.bounds
   
// Color at the top of the gradient.
let topColor: CGColor = UIColor.red.cgColor
    
// Color at the bottom of the gradient.
let bottomColor: CGColor = UIColor.yellow.cgColor
    
// Set colors.
gradientLayer.colors = [topColor, bottomColor]
    
// Set locations of the colors.
gradientLayer.locations = [0.0, 1.0]
    
// Insert gradient layer into view's layer heirarchy.
view.layer.insertSublayer(gradientLayer, at: 0)

Result :

Simple CAGradientLayer.

# Animating a color change in CAGradientLayer.

// Get the current colors of the gradient.
let oldColors = self.gradientLayer.colors
    
// Define the new colors for the gradient.
let newColors = [UIColor.red.cgColor, UIColor.yellow.cgColor]
    
// Set the new colors of the gradient.
self.gradientLayer.colors = newColors
    
// Initialize new animation for changing the colors of the gradient.
let animation: CABasicAnimation = CABasicAnimation(keyPath: "colors")
    
// Set current color value.
animation.fromValue = oldColors
    
// Set new color value.
animation.toValue = newColors
   
// Set duration of animation.
animation.duration = 0.3
    
// Set animation to remove once its completed.
animation.isRemovedOnCompletion = true
    
// Set receiver to remain visible in its final state when the animation is completed.
animation.fillMode = kCAFillModeForwards
    
// Set linear pacing, which causes an animation to occur evenly over its duration.
animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
    
// Set delegate of animation.
animation.delegate = self
    
// Add the animation.
self.gradientLayer.addAnimation(animation, forKey: "animateGradientColorChange")

Result :

Basic CAGradientLayer color change animation.

# Creating a horizontal CAGradientLayer.

// View to hold the CAGradientLayer.
let view: UIView = UIView(frame: CGRect(x: 0, y: 0, width: 320, height: 320))

// Initialize gradient layer.
let gradientLayer: CAGradientLayer = CAGradientLayer()

// Set frame of gradient layer.
gradientLayer.frame = view.bounds

// Color at the top of the gradient.
let topColor: CGColor = UIColor.redColor().CGColor

// Color at the bottom of the gradient.
let bottomColor: CGColor = UIColor.yellowColor().CGColor

// Set colors.
gradientLayer.colors = [topColor, bottomColor]

// Set start point.
gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)

// Set end point.
gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)

// Insert gradient layer into view's layer heirarchy.
view.layer.insertSublayer(gradientLayer, atIndex: 0)

Result :

Horizontal CAGradientLayer.

# Creating a horizontal CAGradientLayer with multiple colors.

// View to hold the CAGradientLayer.
let view: UIView = UIView(frame: CGRect(x: 0, y: 0, width: 320, height: 320))

// Initialize gradient layer.
let gradientLayer: CAGradientLayer = CAGradientLayer()

// Set frame of gradient layer.
gradientLayer.frame = view.bounds

// Color at the top of the gradient.
let topColor: CGColor = UIColor.greenColor().CGColor

// Color at the middle of the gradient.
let middleColor: CGColor = UIColor.blueColor().CGColor

// Color at the bottom of the gradient.
let bottomColor: CGColor = UIColor.blackColor().CGColor

// Set colors.
gradientLayer.colors = [topColor, middleColor, bottomColor]

// Set start point.
gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)

// Set end point.
gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)

// Insert gradient layer into view's layer heirarchy.
view.layer.insertSublayer(gradientLayer, atIndex: 0)

Result :

enter image description here

# Creating a CGGradientLayer with multiple colors.

// View to hold the CAGradientLayer.
let view: UIView = UIView(frame: CGRect(x: 0, y: 0, width: 320, height: 320))
    
// Initialize gradient layer.
let gradientLayer: CAGradientLayer = CAGradientLayer()
    
// Set frame of gradient layer.
gradientLayer.frame = view.bounds
    
// Color at the top of the gradient.
let topColor: CGColor = UIColor.blue.cgColor
    
// Color at the middle of the gradient.
let middleColor: CGColor = UIColor.yellow.cgColor
    
// Color at the bottom of the gradient.
let bottomColor: CGColor = UIColor.green.cgColor
    
// Set colors.
gradientLayer.colors = [topColor, middleColor, bottomColor]
    
// Set locations of the colors.
gradientLayer.locations = [0.0, 0.5, 1.0]
    
// Insert gradient layer into view's layer heirarchy.
view.layer.insertSublayer(gradientLayer, at: 0)

Result :

Complex CAGradientLayer.

# Syntax

  • CAGradientLayer() // Returns an initialized CALayer object.
  • CAGradientLayer(layer: layer) // Override to copy or initialize custom fields of the specified layer.

# Parameters

Parameter Details
color An array of CGColorRef objects defining the color of each gradient stop. Animatable.
locations An optional array of NSNumber objects defining the location of each gradient stop. Animatable.
endPoint The end point of the gradient when drawn in the layer’s coordinate space. Animatable.
startPoint The start point of the gradient when drawn in the layer’s coordinate space. Animatable.
type Style of gradient drawn by the layer. Defaults to kCAGradientLayerAxial.

# Remarks

  • Use startPoint and endPoint to change the orientation of the CAGradientLayer.
  • Use the locations to affect the spread/positions of the colors.