Background Color Animation

[RodolfoAntonici]

Hey there,
Im having an issue with the IFTTTColorAnimation

    var gradientBarColorAnimation: IFTTTColorAnimation!

    public override func viewDidLoad() {
        super.viewDidLoad()

        var myView = UIView(frame: CGRectMake(0, 0, 100, 100));
        myView.backgroundColor = UIColor.blackColor()
        self.view.addSubview(myView)

        self.gradientBarColorAnimation = IFTTTColorAnimation(view: myView)
        self.gradientBarColorAnimation.addKeyframeForTime(0, color: myView.backgroundColor)
        self.gradientBarColorAnimation.addKeyframeForTime(64, color: UIColor.redColor())
    }

    public func scrollViewDidScroll(scrollView: UIScrollView) {

        self.gradientBarColorAnimation.animate(scrollView.contentOffset.y)
    }

The problem is: when it pass the 64 time, it just changes the color to red, isn't an animated transition.
I tried to change the colors alpha chanel as the example uses, it doesn't work either.

Aditional info:
iOS 8.4,
Xcode 6.4
Swift 1.2

[gazsp]

I have the same issue with JazzHands 2.0, although the demo app works fine.

scrollViewDidScroll uses the default implementation from IFTTTAnimatedPagingScrollViewController.

[gazsp]

The issue is in IFTTTFilmStrip.m here (see the commented out line):

- (id<IFTTTInterpolatable>)valueAtTime:(CGFloat)time
{
    NSAssert(!self.isEmpty, @"At least one KeyFrame must be set before animation begins.");
    id value;
    NSUInteger indexAfter = [self indexOfKeyframeAfterTime:time];
    if (indexAfter == 0) {
        value = ((IFTTTKeyframe *)self.keyframes[0]).value;
    } else if (indexAfter < self.keyframes.count) {
        IFTTTKeyframe *keyframeBefore = (IFTTTKeyframe *)self.keyframes[indexAfter - 1];
        IFTTTKeyframe *keyframeAfter = (IFTTTKeyframe *)self.keyframes[indexAfter];
        CGFloat progress = [self progressFromTime:keyframeBefore.time toTime:keyframeAfter.time atTime:time withEasingFunction:keyframeBefore.easingFunction];
        if ([keyframeBefore.value respondsToSelector:@selector(interpolateTo:withProgress:)]
//            && [keyframeAfter.value isKindOfClass:[keyframeBefore.value class]]
        ) {
            value = [keyframeBefore.value interpolateTo:keyframeAfter.value withProgress:progress];
        } else {
            value = keyframeBefore.value;
        }
    } else {
        value = ((IFTTTKeyframe *)self.keyframes.lastObject).value;
    }
    return value;
}

This is because [UIColor blackColor] has a class of UIDeviceWhiteColor, where as any other non white / black / grey colours will have a class of UIDeviceRGBColor. This makes the if statement fail, and hence the interpolation.

[lauraskelton]

@RodolfoAntonici Thanks for pointing out the issue, and @gazsp thanks for the super helpful detective work on the cause!