[英]How to draw a line in Swift 3
I would like the user to touch 2 points and then a line is drawn between those two points. 我希望用户触摸2个点,然后在这两个点之间绘制一条线。 Here is what I have so far: 这是我到目前为止:
func drawline(){
let context = UIGraphicsGetCurrentContext()
context!.beginPath()
context?.move(to: pointA)
context?.addLine(to: pointB)
context!.strokePath()
}
pointA
is the first point the user touched and pointB
is the second point. pointA
是第一点的用户触摸和pointB
是第二点。 I get the error: 我收到错误:
thread 1:EXC_BREAKPOINT
Thanks in advance for your help. 在此先感谢您的帮助。
To draw a line between two points the first thing you need is get the CGPoints
from the current UIView
, there are several ways of achieve this. 要在两点之间画一条线,首先需要从当前的UIView
获取CGPoints
,有几种方法可以实现这一点。 I going to use an UITapGestureRecognizer
for the sake of the sample to detect when you make a tap. 我将使用UITapGestureRecognizer
以便样本在您点击时进行检测。
The another step is once you have the two points saved draw the line between the two points, and for this again you can use the graphics context as you try before or use CAShapeLayer
. 另一个步骤是,一旦你保存了两点就画两点之间的线,为此你可以再次使用图形上下文或者使用CAShapeLayer
。
So translating the explained above we get the following code: 所以翻译上面解释的我们得到以下代码:
class ViewController: UIViewController {
var tapGestureRecognizer: UITapGestureRecognizer!
var firstPoint: CGPoint?
var secondPoint: CGPoint?
override func viewDidLoad() {
super.viewDidLoad()
tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(self.showMoreActions(touch:)))
tapGestureRecognizer.numberOfTapsRequired = 1
view.addGestureRecognizer(tapGestureRecognizer)
}
func showMoreActions(touch: UITapGestureRecognizer) {
let touchPoint = touch.location(in: self.view)
guard let _ = firstPoint else {
firstPoint = touchPoint
return
}
guard let _ = secondPoint else {
secondPoint = touchPoint
addLine(fromPoint: firstPoint!, toPoint: secondPoint!)
firstPoint = nil
secondPoint = nil
return
}
}
func addLine(fromPoint start: CGPoint, toPoint end:CGPoint) {
let line = CAShapeLayer()
let linePath = UIBezierPath()
linePath.move(to: start)
linePath.addLine(to: end)
line.path = linePath.cgPath
line.strokeColor = UIColor.red.cgColor
line.lineWidth = 1
line.lineJoin = kCALineJoinRound
self.view.layer.addSublayer(line)
}
}
The above code is going to draw a line every time two points are selected and you can customize the above function as you like. 每次选择两个点时,上面的代码将绘制一条线,您可以根据需要自定义上述功能。
I hope this help you. 我希望这对你有帮助。
Draw line in Swift 4.1 在Swift 4.1中绘制线条
class MyViewController: UIViewController {
@IBOutlet weak var imgViewDraw: UIImageView!
var lastPoint = CGPoint.zero
var red: CGFloat = 0.0
var green: CGFloat = 0.0
var blue: CGFloat = 0.0
var brushWidth: CGFloat = 10.0
var opacity: CGFloat = 1.0
var isSwiping:Bool!
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
//MARK: Touch events
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
isSwiping = false
if let touch = touches.first{
lastPoint = touch.location(in: imgViewDraw)
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
isSwiping = true;
if let touch = touches.first{
let currentPoint = touch.location(in: imgViewDraw)
UIGraphicsBeginImageContext(self.imgViewDraw.frame.size)
self.imgViewDraw.image?.draw(in: CGRect(x:0, y:0,width:self.imgViewDraw.frame.size.width, height:self.imgViewDraw.frame.size.height))
UIGraphicsGetCurrentContext()?.move(to: CGPoint(x: lastPoint.x, y: lastPoint.y))
UIGraphicsGetCurrentContext()?.addLine(to: CGPoint(x: currentPoint.x, y: currentPoint.y))
UIGraphicsGetCurrentContext()?.setLineCap(CGLineCap.round)
UIGraphicsGetCurrentContext()?.setLineWidth(self.brushWidth)
UIGraphicsGetCurrentContext()?.setStrokeColor(red: red, green: green, blue: blue, alpha: 1.0)
UIGraphicsGetCurrentContext()?.strokePath()
self.imgViewDraw.image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
lastPoint = currentPoint
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
if(!isSwiping) {
// This is a single touch, draw a point
UIGraphicsBeginImageContext(self.imgViewDraw.frame.size)
self.imgViewDraw.image?.draw(in: CGRect(x:0, y:0,width:self.imgViewDraw.frame.size.width, height:self.imgViewDraw.frame.size.height))
UIGraphicsGetCurrentContext()?.setLineCap(CGLineCap.round)
UIGraphicsGetCurrentContext()?.setLineWidth(self.brushWidth)
UIGraphicsGetCurrentContext()?.move(to: CGPoint(x: lastPoint.x, y: lastPoint.y))
UIGraphicsGetCurrentContext()?.addLine(to: CGPoint(x: lastPoint.x, y: lastPoint.y))
UIGraphicsGetCurrentContext()?.setStrokeColor(red: red, green: green, blue: blue, alpha: 1.0)
UIGraphicsGetCurrentContext()?.strokePath()
self.imgViewDraw.image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
}
}
}
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