How can I prevent closing Bezier Path

问题

I want to create a Bezier curve, and create a collision boundary for my object.

let firstSurfacePoint = CGPoint(x: 30, y: 120)
let secondSurfacePoint = CGPoint(x: 20, y: 200)
let thirdSurfacePoint = CGPoint(x: 200, y: 300)

let center = CGPoint(x: 150, y: 120)
let radius: CGFloat = 120.00
let arcWidth: CGFloat = 20.00    
let fourthSurfacePoint = CGPoint(x: 240, y: 300)

func createCollisionPath(collision: UICollisionBehavior) {

    let line =  UIBezierPath()

    line.moveToPoint(firstSurfacePoint)
    line.addCurveToPoint(thirdSurfacePoint, controlPoint1: secondSurfacePoint, controlPoint2: secondSurfacePoint)
    line.addLineToPoint(fourthSurfacePoint)

    let currentPath = CAShapeLayer()
    currentPath.path = line.CGPath
    currentPath.strokeColor = UIColor.blackColor().CGColor
    currentPath.fillColor = UIColor.clearColor().CGColor
    currentPath.lineWidth = 1
    view.layer.addSublayer(currentPath)

    collision.addBoundaryWithIdentifier("curve", forPath: line)

}

the same poor result I get, if I choose addArcWithCente

line.moveToPoint(firstSurfacePoint)
line.addArcWithCenter(center, radius: radius, startAngle: CGFloat(M_PI), endAngle: CGFloat(M_PI/2), clockwise: false)
line.addLineToPoint(fourthSurfacePoint)

In this two tries receive a strange results, that are crucial, as I can't create a proper collision. In the first attempt my object goes through path as if it is a straight line from firstPoint to thirdPoint, as well as in the second

What am I doing wrong?

My figure(without Arc)

My figure(with Arc)

回答1:

currentPath.fillColor = nil

currentPath.fillColor = UIColor.clearColor().CGColor

来源：https://stackoverflow.com/questions/42006716/how-can-i-prevent-closing-bezier-path

标签

swift

uibezierpath

cgpoint