Draw lines in swift 3.0 - ios

Question

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()
}

Answer 1

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)
}
}

Answer 2

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()
}
}