iOS
CAGradientLayer

Sintassi

• CAGradientLayer () // Restituisce un oggetto CALayer inizializzato.
• CAGradientLayer (layer: layer) // Override per copiare o inizializzare i campi personalizzati del layer specificato.

Parametri

Osservazioni

Creazione di un 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)

Risultato:

Creazione di un CGGradientLayer con più colori.

// 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)

Risultato:

Creazione di un CAGradientLayer orizzontale.

// 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)

Risultato:

Creazione di un CAGradientLayer orizzontale con più colori.

// 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)

Risultato:

Animazione di un cambiamento di colore 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")

Risultato: