swift - Swift 中的 UIBezierPath 描边(和填充)

Question

我正在努力寻找一种快速绘制(和填充)贝塞尔曲线路径的方法。这是我认为行得通但行不通的方法。

var myBezier = UIBezierPath()
myBezier.moveToPoint(CGPoint(x: 0, y: 0))
myBezier.addLineToPoint(CGPoint(x: 100, y: 0))
myBezier.addLineToPoint(CGPoint(x: 50, y: 100))
myBezier.closePath()
UIColor.setStroke(UIColor.blackColor())
myBezier.stroke()

行 UIColor.setStroke(UIColor.blackColor()) 在控制台中给我这个错误:

Playground execution failed: error: <REPL>:51:1: error: expression
resolves to an unused function UIColor.blackColor())
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

行 myBezier.stroke() 给我这组错误:

Jul 19 12:07:46 Computer-MacBook-Pro.local [20579] <Error>: CGContextSaveGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 19 12:07:46 Computer-MacBook-Pro.local [20579] <Error>: CGContextSetLineWidth: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 19 12:07:46 Computer-MacBook-Pro.local [20579] <Error>: CGContextSetLineJoin: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 19 12:07:46 Computer-MacBook-Pro.local [20579] <Error>: CGContextSetLineCap: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 19 12:07:46 Computer-MacBook-Pro.local [20579] <Error>: CGContextSetMiterLimit: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 19 12:07:46 Computer-MacBook-Pro.local [20579] <Error>: CGContextSetFlatness: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 19 12:07:46 Computer-MacBook-Pro.local [20579] <Error>: CGContextAddPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 19 12:07:46 Computer-MacBook-Pro.local [20579] <Error>: CGContextDrawPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 19 12:07:46 Computer-MacBook-Pro.local [20579] <Error>: CGContextRestoreGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

在 Objective-C 中，我会使用这样的东西，但是，这在 Swift 中显然行不通。

[[UIColor blackColor] setStroke]
[myBezier stroke]

有什么建议吗？

Answer 1

setStroke 是 UIColor 的实例方法，不带参数。使用

  UIColor.blackColor().setStroke()

这意味着:

    var color = UIColor.blackColor()   //returns color
    color.setStroke()                  // setStroke on color

但你做的恰恰相反。

 UIColor.setStroke(UIColor.blackColor())

这意味着您正在调用UIColor 的类方法setStroke，并传递blackColor。 setStroke是一个实例方法，不是类方法，所以你需要一个UIColor对象，它由UIColor.blackColor()返回。

编辑

//MyPlayground.playground
import UIKit

class MyCustomView :UIView{


    //Write your code in drawRect
    override func drawRect(rect: CGRect) {
        var myBezier = UIBezierPath()
        myBezier.moveToPoint(CGPoint(x: 0, y: 0))
        myBezier.addLineToPoint(CGPoint(x: 100, y: 0))
        myBezier.addLineToPoint(CGPoint(x: 50, y: 100))
        myBezier.closePath()
        UIColor.blackColor().setStroke()
        myBezier.stroke()
    }


}

var view = MyCustomView(frame: CGRectMake(0, 0, 100, 100))
view.backgroundColor = UIColor.whiteColor()

这不会给出上下文错误