xcode 使用 UIBezierPath 在 Swift 3.x 中画一条线
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Drawing a line in Swift 3.x with UIBezierPath
提问by Tristan G
I am trying to draw a line on an UIView with an UIBezierpath. I think I am missing something, but wasn't able to find it out.
我试图用 UIBezierpath 在 UIView 上画一条线。我想我错过了一些东西，但无法找到它。
Here is my code:
这是我的代码：
// Code for touch recognition
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
swiped = false
if let touch = touches.first as? UITouch? {
lastPoint = (touch?.location(in: fullview))!
//print(lastPoint)
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
swiped = true
if let touch = touches.first as? UITouch? {
let currentPoint = touch?.location(in: fullview)
drawLineFrom(fromPoint: lastPoint, toPoint: currentPoint!)
lastPoint = currentPoint!
//print(lastPoint)
//print("touch moved")
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
if !swiped {
drawLineFrom(fromPoint: lastPoint, toPoint: lastPoint)
}
//print("touch ended")
}
//code for drawing
func drawLineFrom(fromPoint: CGPoint, toPoint: CGPoint){
UIGraphicsBeginImageContext(fullview.frame.size)
let context = UIGraphicsGetCurrentContext()
let aPath = UIBezierPath()
//aPath.move(to: fromPoint)
//aPath.addLine(to: toPoint)
aPath.lineWidth=10.0
aPath.lineJoinStyle = .round
aPath.move(to: CGPoint(x:15,y:15))
aPath.addLine(to: CGPoint(x:80,y:80))
aPath.addClip()
aPath.close()
UIColor.green.set()
aPath.stroke()
//print("drawline")
//print("Frompoint = ",fromPoint)
//print("topoint = ",toPoint)
/* context?.setLineCap(.round)
context?.setLineWidth(brushWidth)
context?.setStrokeColor(red: red, green: green, blue: blue, alpha: 1.0)
context?.setBlendMode(.normal)
context?.beginPath()
context?.move(to: fromPoint)
context?.addLine(to: toPoint)
context?.closePath()
context?.strokePath()*/
//let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
fullview.setNeedsDisplay()
}
As you can see, I tried it also with the context, but it wasn't working too.
如您所见，我也在上下文中尝试了它，但它也不起作用。
回答by Mar-k
I use this to draw a line:
我用它来画一条线：
let doYourPath = UIBezierPath(rect: CGRect(x: xPos, y: yPos, width: yourWidth, height: yourHeight))
let layer = CAShapeLayer()
layer.path = doYourPath.cgPath
layer.strokeColor = UIColor.white.cgColor
layer.fillColor = UIColor.white.cgColor
self.view.layer.addSublayer(layer)
Hope this help you out. This is just one the way to draw a line in swift.
希望这能帮到你。这只是快速画线的一种方式。
回答by hnh
Well, you are drawing into an image context (an offscreen bitmap), not into the view. That is quite likely not what you want? Make sure you have read iOS Drawing Concepts.
好吧，您正在绘制图像上下文（屏幕外位图），而不是视图。那很可能不是您想要的？确保您已阅读iOS 绘图概念。
Your UIViewsubclass should probably just track the positions of the touches (like in a var touchedPositions = [CGPoint]()) and call setNeedsDisplay().
Then implement the func draw(_ rect: CGRect)method in your subclass. Within this method, create your path and draw it according to the positions you tracked (w/o creating a new context).
您的UIView子类可能应该只跟踪触摸的位置（如在 a 中var touchedPositions = [CGPoint]()）并调用setNeedsDisplay(). 然后func draw(_ rect: CGRect)在您的子类中实现该方法。在此方法中，创建您的路径并根据您跟踪的位置绘制它（不创建新上下文）。
