Why doesn't UIView.animateWithDuration affect this custom view? - swift

Question

I designed a custom header view that masks an image and draws a border on the bottom edge, which is an arc. It looks like this:
Here's the code for the class:
class HeaderView: UIView
{
private let imageView = UIImageView()
private let dimmerView = UIView()
private let arcShape = CAShapeLayer()
private let maskShape = CAShapeLayer() // Masks the image and the dimmer
private let titleLabel = UILabel()
#IBInspectable var image: UIImage? { didSet { self.imageView.image = self.image } }
#IBInspectable var title: String? { didSet {self.titleLabel.text = self.title} }
#IBInspectable var arcHeight: CGFloat? { didSet {self.setupLayers()} }
// MARK: Initialization
override init(frame: CGRect)
{
super.init(frame:frame)
initMyStuff()
}
required init?(coder aDecoder: NSCoder)
{
super.init(coder:aDecoder)
initMyStuff()
}
override func prepareForInterfaceBuilder()
{
backgroundColor = UIColor.clear()
}
internal func initMyStuff()
{
backgroundColor = UIColor.clear()
titleLabel.font = Font.AvenirNext_Bold(24)
titleLabel.text = "TITLE"
titleLabel.textColor = UIColor.white()
titleLabel.layer.shadowColor = UIColor.black().cgColor
titleLabel.layer.shadowOffset = CGSize(width: 0.0, height: 2.0)
titleLabel.layer.shadowRadius = 0.0;
titleLabel.layer.shadowOpacity = 1.0;
titleLabel.layer.masksToBounds = false
titleLabel.layer.shouldRasterize = true
imageView.contentMode = UIViewContentMode.scaleAspectFill
addSubview(imageView)
dimmerView.frame = self.bounds
dimmerView.backgroundColor = UIColor(red: 0, green: 0, blue: 0, alpha: 0.6)
addSubview(dimmerView)
addSubview(titleLabel)
// Add the shapes
self.layer.addSublayer(arcShape)
self.layer.addSublayer(maskShape)
self.layer.masksToBounds = true // This seems to be unneeded...test more
// Set constraints
imageView.translatesAutoresizingMaskIntoConstraints = false
imageView .autoPinEdgesToSuperviewEdges()
titleLabel.autoCenterInSuperview()
}
func setupLayers()
{
let aHeight = arcHeight ?? 10
// Create the arc shape
arcShape.path = AppocalypseUI.createHorizontalArcPath(CGPoint(x: 0, y: bounds.size.height), width: bounds.size.width, arcHeight: aHeight)
arcShape.strokeColor = UIColor.white().cgColor
arcShape.lineWidth = 1.0
arcShape.fillColor = UIColor.clear().cgColor
// Create the mask shape
let maskPath = AppocalypseUI.createHorizontalArcPath(CGPoint(x: 0, y: bounds.size.height), width: bounds.size.width, arcHeight: aHeight, closed: true)
maskPath.moveTo(nil, x: bounds.size.width, y: bounds.size.height)
maskPath.addLineTo(nil, x: bounds.size.width, y: 0)
maskPath.addLineTo(nil, x: 0, y: 0)
maskPath.addLineTo(nil, x: 0, y: bounds.size.height)
//let current = CGPathGetCurrentPoint(maskPath);
//print(current)
let mask_Dimmer = CAShapeLayer()
mask_Dimmer.path = maskPath.copy()
maskShape.fillColor = UIColor(red: 0, green: 0, blue: 0, alpha: 1.0).cgColor
maskShape.path = maskPath
// Apply the masks
imageView.layer.mask = maskShape
dimmerView.layer.mask = mask_Dimmer
}
override func layoutSubviews()
{
super.layoutSubviews()
// Let's go old school here...
imageView.frame = self.bounds
dimmerView.frame = self.bounds
setupLayers()
}
}
Something like this will cause it to just snap to the new size without gradually changing its frame:
UIView.animate(withDuration: 1.0)
{
self.headerView.arcHeight = self.new_headerView_arcHeight
self.headerView.frame = self.new_headerView_frame
}
I figure it must have something to do with the fact that I'm using CALayers, but I don't really know enough about what's going on behind the scenes.
EDIT:
Here's the function I use to create the arc path:
class func createHorizontalArcPath(_ startPoint:CGPoint, width:CGFloat, arcHeight:CGFloat, closed:Bool = false) -> CGMutablePath
{
// http://www.raywenderlich.com/33193/core-graphics-tutorial-arcs-and-paths
let arcRect = CGRect(x: startPoint.x, y: startPoint.y-arcHeight, width: width, height: arcHeight)
let arcRadius = (arcRect.size.height/2) + (pow(arcRect.size.width, 2) / (8*arcRect.size.height));
let arcCenter = CGPoint(x: arcRect.origin.x + arcRect.size.width/2, y: arcRect.origin.y + arcRadius);
let angle = acos(arcRect.size.width / (2*arcRadius));
let startAngle = CGFloat(M_PI)+angle // (180 degrees + angle)
let endAngle = CGFloat(M_PI*2)-angle // (360 degrees - angle)
// let startAngle = radians(180) + angle;
// let endAngle = radians(360) - angle;
let path = CGMutablePath();
path.addArc(nil, x: arcCenter.x, y: arcCenter.y, radius: arcRadius, startAngle: startAngle, endAngle: endAngle, clockwise: false);
if(closed == true)
{path.addLineTo(nil, x: startPoint.x, y: startPoint.y);}
return path;
}
BONUS:
Setting the arcHeight property to 0 results in no white line being drawn. Why?

Answer 1

The Path property can't be animated. You have to approach the problem differently. You can draw an arc 'instantly', any arc, so that tells us that we need to handle the animation manually. If you expect the entire draw process to take say 3 seconds, then you might want to split the process to 1000 parts, and call the arc drawing function 1000 times every 0.3 miliseconds to draw the arc again from the beginning to the current point.

Answer 2

self.headerView.arcHeight is not a animatable property. It is only UIView own properties are animatable
you can do something like this
let displayLink = CADisplayLink(target: self, selector: #selector(update))
displayLink.addToRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode
let expectedFramesPerSecond = 60
var diff : CGFloat = 0
func update() {
let diffUpdated = self.headerView.arcHeight - self.new_headerView_arcHeight
let done = (fabs(diffUpdated) < 0.1)
if(!done){
self.headerView.arcHeight -= diffUpdated/(expectedFramesPerSecond*0.5)
self.setNeedsDisplay()
}
}