Trim UIView with 2 arcs - ios

Question

I have a UIView and I want to trim it with two circles, like I've drawn(sorry for the quality).
My code:
final class TrimmedView: UIView {
override init(frame: CGRect) {
super.init(frame: frame)
let size = CGSize(width: 70, height: 70)
let innerRadius: CGFloat = 366.53658283002471
let innerBottomRadius: CGFloat = 297.88543112651564
let path = UIBezierPath()
path.move(to: CGPoint(x: -innerRadius + (size.width / 2), y: innerRadius))
path.addArc(withCenter: CGPoint(x: size.width / 2, y: innerRadius), radius: innerRadius, startAngle: CGFloat.pi, endAngle: 0, clockwise: true)
path.move(to: CGPoint(x: -innerBottomRadius + (size.width / 2), y: innerBottomRadius))
path.addArc(withCenter: CGPoint(x: size.width / 2, y: innerBottomRadius), radius: innerBottomRadius, startAngle: 0, endAngle: CGFloat.pi, clockwise: true)
path.close()
let shapeLayer = CAShapeLayer()
shapeLayer.path = path.cgPath
shapeLayer.shadowPath = path.cgPath
layer.mask = shapeLayer
}
required init?(coder: NSCoder) {
super.init(coder: coder)
}
}
ViewController:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let view = UIView(frame: CGRect(origin: CGPoint(x: (self.view.bounds.width - 70) / 2, y: (self.view.bounds.height - 70) / 2), size: CGSize(width: 70, height: 70)))
view.backgroundColor = .red
self.view.addSubview(view)
let view1 = TrimmedView(frame: view.frame)
view1.backgroundColor = .yellow
self.view.addSubview(view1)
}
I got this result. It seems for me that top trimming works but the bottom doesn't and I don't know why. Any help would be appreciated. Thanks.

Answer 1

Here is a custom view that should give you what you want.
The UIBezierPath uses QuadCurves for the top "convex" arc and the bottom "concave" arc.
It is marked #IBDesignable so you can see it at design-time in IB / Storyboard. The "height" of the arc and the fill color are each set as #IBInspectable so you can adjust those values at design-time as well.
To use it in Storyboard:
Add a normal UIView
change the Class to BohdanShapeView
in the Attributes Inspector pane, set the Arc Offset and the Fill Color
set the background color as with a normal view (you'll probably use clear)
Result:
To use it via code:
let view1 = BohdanShapeView(frame: view.frame)
view1.fillColor = .systemTeal
view1.arcOffset = 10
self.view.addSubview(view1)
Here is the class:
#IBDesignable
class BohdanShapeView: UIView {
#IBInspectable var arcOffset: CGFloat = 0.0
#IBInspectable var fillColor: UIColor = UIColor.white
let shapeLayer = CAShapeLayer()
override init(frame: CGRect) {
super.init(frame: frame)
commonInit()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
commonInit()
}
func commonInit() -> Void {
// add the shape layer
layer.addSublayer(shapeLayer)
}
override func layoutSubviews() {
super.layoutSubviews()
// fill color for the shape
shapeLayer.fillColor = self.fillColor.cgColor
let width = bounds.size.width
let height = bounds.size.height
let bezierPath = UIBezierPath()
// start at arcOffset below top-left
bezierPath.move(to: CGPoint(x: 0.0, y: 0.0 + arcOffset))
// add curve to arcOffset below top-right
bezierPath.addQuadCurve(to: CGPoint(x: width, y: 0.0 + arcOffset), controlPoint: CGPoint(x: width * 0.5, y: 0.0 - arcOffset))
// add line to bottom-right
bezierPath.addLine(to: CGPoint(x: width, y: height))
// add curve to bottom-left
bezierPath.addQuadCurve(to: CGPoint(x: 0.0, y: height), controlPoint: CGPoint(x: width * 0.5, y: height - arcOffset * 2.0))
// close the path
bezierPath.close()
shapeLayer.path = bezierPath.cgPath
}
}