swift UIBezierPath 碰撞边界问题（UIKit 动力学）

Question

您好，我有一个应用程序，用户可以在其中用手指绘制一条贝塞尔曲线路径，并将其指定为坠落物体的碰撞边界。它有效！...但是！贝塞尔曲线似乎正在关闭路径（隐藏），这也成为边界。

所以，如果我画一条凸曲线，它就完美了。但是如果我画一条凹曲线，物体就不会进入曲线。任何帮助表示赞赏。我需要以某种方式打开曲线！下面的代码

override func draw(_ rect: CGRect) {
         super.draw(rect)
         
       guard let context = UIGraphicsGetCurrentContext() else {
             return
         }
         
         animator = UIDynamicAnimator(referenceView: self)
         gravity = UIGravityBehavior()
         animator.addBehavior(gravity)
         gravity.gravityDirection = CGVector(dx: 0, dy: 0.1)
         collision = UICollisionBehavior(items: [hamburger])
         collision.collisionDelegate = self
         collision.addBoundary(withIdentifier: "belt" as NSCopying, for: UIBezierPath(rect: belt.frame))
         
         animator.addBehavior(collision)

     
         
         collision.addItem(hamburger)
         gravity.addItem(hamburger)
         
         collision.translatesReferenceBoundsIntoBoundary = true
         
         let itemBehaviour = UIDynamicItemBehavior(items: [hamburger])
         itemBehaviour.elasticity = 0.1
         animator.addBehavior(itemBehaviour)
         
         
         lines.forEach { (line) in
             for (i, p) in (line.points?.enumerated())! {
                 if i == 0 {
                     context.move(to: p)
                 } else {
                     context.addLine(to: p)
                 }
                 context.setStrokeColor(line.color?.withAlphaComponent(line.opacity ?? 1.0).cgColor ?? UIColor.systemBlue.cgColor)
                 context.setLineWidth(line.width ?? 10.0)
                 lineboundary = UIBezierPath(cgPath: context.path!)
                 collision.addBoundary(withIdentifier: "linedrawn" as NSCopying, for: lineboundary)
             }
             context.setLineCap(.round)
             context.strokePath()
        
         }
         
         
         
     }

Answer 1

UIKit Dynamics 不允许凹路径。但您可以将它们添加为单独的 UICollisionBehavior 个实例：

for index in points.indices.dropFirst() {
    let path = UIBezierPath()
    path.move(to: points[index-1])
    path.addLine(to: points[index])

    let collision = UICollisionBehavior(items: [droppedView])
    collision.addBoundary(withIdentifier: "\(index)" as NSString, for: path)
    animator.addBehavior(collision)
}

这导致：

swift UIBezierPath 碰撞边界问题（UIKit 动力学）

swift UIBezierPath collision boundary issues ( UIKit Dynamics )

swift

collision

uibezierpath

uikit-dynamics