Re-Animate Gradient Background with different color in swift in ios
<p>I want to re-animate gradient background with different color when animating.
I can successfully animate gradient color with this code.</p>

<pre><code>let dayTopColor = CommonUtils.colorWithHexString("955EAC")
let dayBottomColor = CommonUtils.colorWithHexString("9F3050")
let dayToTopColor = CommonUtils.colorWithHexString("D15B52")
let dayToBottomColor = CommonUtils.colorWithHexString("CC4645")
let nightTopColor = CommonUtils.colorWithHexString("2D5E7C")
let nightBottomColor = CommonUtils.colorWithHexString("19337D")
let nightToTopColor = CommonUtils.colorWithHexString("21334E")
let nightToBottomColor = CommonUtils.colorWithHexString("101A55")
var isInSaudiArabia = false
var gradient : CAGradientLayer?
var toColors : AnyObject?
var fromColors : AnyObject?

func animateBackground(){
        var layerToRemove: CAGradientLayer?
        for layer in self.view.layer.sublayers!{
            if layer.isKindOfClass(CAGradientLayer) {
                layerToRemove = layer as? CAGradientLayer
            }
        }
        layerToRemove?.removeFromSuperlayer()

            self.gradient!.colors = [nightTopColor.CGColor, nightBottomColor.CGColor]
            self.toColors = [nightToTopColor.CGColor, nightToBottomColor.CGColor]

        self.view.layer.insertSublayer(self.gradient!, atIndex: 0)
        animateLayer()
    }

    func animateLayer(){

        self.fromColors = self.gradient!.colors!
        self.gradient!.colors = self.toColors as? [AnyObject]
        let animation : CABasicAnimation = CABasicAnimation(keyPath: "colors")
        animation.delegate = self
        animation.fromValue = fromColors
        animation.toValue = toColors
        animation.duration = 3.50
        animation.removedOnCompletion = true
        animation.fillMode = kCAFillModeForwards
        animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
        animation.delegate = self

        self.gradient!.addAnimation(animation, forKey:"animateGradient")
    }

    override func animationDidStop(anim: CAAnimation, finished flag: Bool) {

        self.toColors = self.fromColors;
        self.fromColors = self.gradient!.colors!

        animateLayer()
    }
</code></pre>

<p>CommonUtils.colorWithHexString() is a function which converts hex color to UIColor.
Btw when i try to change background color to day color while animating, background gradient color got flickered.</p>

<p>Is there anybody who knows solution.</p>