获取UIBezier路径的起点

Question

我创建了一个UIBezierPath，但我不知道如何访问它的起点。我试着这样做：

let startPoint = path.currentPoint 

酒店currentPoint给我的最后一个点，而不是起点。我需要起点的原因是因为我想在路径的起始点放置图像。

任何想法？

Answer 1

您需要下拉到CGPath并使用CGPathApply来遍历元素。你只需要第一个，但你必须全部看。

我假设你的路径格式良好，并以“移动”开始。这应该永远是正确的UIBezierPath（我不知道有任何办法让它不会是真的。）

你需要从抢mayoff的CGPath.forEach，这是相当棘手的一些帮助，但在地方这是非常简单的：

// rob mayoff's CGPath.foreach 
extension CGPath { 
    func forEach(@noescape body: @convention(block) (CGPathElement) -> Void) { 
     typealias Body = @convention(block) (CGPathElement) -> Void 
     func callback(info: UnsafeMutablePointer<Void>, element: UnsafePointer<CGPathElement>) { 
      let body = unsafeBitCast(info, Body.self) 
      body(element.memory) 
     } 
     let unsafeBody = unsafeBitCast(body, UnsafeMutablePointer<Void>.self) 
     CGPathApply(self, unsafeBody, callback) 
    } 
} 

// Finds the first point in a path 
extension UIBezierPath { 
    func firstPoint() -> CGPoint? { 
     var firstPoint: CGPoint? = nil 

     self.CGPath.forEach { element in 
      // Just want the first one, but we have to look at everything 
      guard firstPoint == nil else { return } 
      assert(element.type == .MoveToPoint, "Expected the first point to be a move") 
      firstPoint = element.points.memory 
     } 
     return firstPoint 
    } 
} 

---

在斯威夫特3，它基本上是相同的：

// rob mayoff's CGPath.foreach 
extension CGPath { 
    func forEach(body: @convention(block) (CGPathElement) -> Void) { 
     typealias Body = @convention(block) (CGPathElement) -> Void 
     func callback(info: UnsafeMutableRawPointer?, element: UnsafePointer<CGPathElement>) { 
      let body = unsafeBitCast(info, to: Body.self) 
      body(element.pointee) 
     } 
     let unsafeBody = unsafeBitCast(body, to: UnsafeMutableRawPointer.self) 
     self.apply(info: unsafeBody, function: callback) 
    } 
} 

// Finds the first point in a path 
extension UIBezierPath { 
    func firstPoint() -> CGPoint? { 
     var firstPoint: CGPoint? = nil 

     self.cgPath.forEach { element in 
      // Just want the first one, but we have to look at everything 
      guard firstPoint == nil else { return } 
      assert(element.type == .moveToPoint, "Expected the first point to be a move") 
      firstPoint = element.points.pointee 
     } 
     return firstPoint 
    } 
} 

Answer 2

简单的方法是

-Subclass的UIBezierPath

- 创建自定义属性为的startPoint

-override的moveToPoint方法和设定值的startPoint有

class MyBezierPath: UIBezierPath { 
    var startPoint :CGPoint? 

    override func moveToPoint(point: CGPoint) { 
     super.moveToPoint(point) 
     startPoint=point; 
    } 
} 

    var myBezier = MyBezierPath() 
    myBezier.moveToPoint(CGPoint(x: 0, y: 0)) 
    myBezier.addLineToPoint(CGPoint(x: 100, y: 0)) 
    myBezier.addLineToPoint(CGPoint(x: 50, y: 100))