Agfdhyk

I used the following code to no avail in Swift 3.0 - it gives me a blank screen on the simulator - I don't know what's happening.

import UIKit



class DrawExample: UIView {



        override func draw( _ rect: CGRect) {



        let context = UIGraphicsGetCurrentContext()

        context!.setLineWidth(3.0)

        context!.setStrokeColor(UIColor.purple.cgColor)



        //make and invisible path first then we fill it in

        context!.move(to: CGPoint(x: 50, y: 60))

        context!.addLine(to: CGPoint(x: 250, y:320))

        context!.strokePath()

    }

Update your class with below:

import UIKit



class DrawExample: UIView {



    override init(frame: CGRect) {

        super.init(frame: frame)

    }



    required init?(coder aDecoder: NSCoder) {

        fatalError("init(coder:) has not been implemented")

    }



    override func draw( _ rect: CGRect) {

        let context = UIGraphicsGetCurrentContext()

        context!.setLineWidth(3.0)

        context!.setStrokeColor(UIColor.purple.cgColor)



        //make and invisible path first then we fill it in

        context!.move(to: CGPoint(x: 50, y: 60))

        context!.addLine(to: CGPoint(x: 250, y:320))

        context!.strokePath()

    }

}

Now make an instance on the view controller and add it to view. Check the below code for it.

import UIKit



class ViewController: UIViewController {



    override func viewDidLoad() {

        super.viewDidLoad()

        // Do any additional setup after loading the view, typically from a nib.



        let draw = DrawExample(frame: self.view.bounds)

        view.addSubview(draw)

    }    

}

Drawing in Swift 4.1

let lastPoint = CGPoint.zero

let red: CGFloat = 0.0

let green: CGFloat = 0.0

let blue: CGFloat = 0.0

let brushWidth: CGFloat = 10.0

let opacity: CGFloat = 1.0

var isSwiping:Bool!

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()

    }

}