Implement ink annotations on iOS 11 PDFKit document

Question

I want to allow the user to draw on an iOS 11 PDFKit document viewed in a PDFView. The drawing should ultimately be embedded inside the PDF.

The latter I have solved by

Answer 1

I've done this by creating a new view class (eg Annotate View) and putting on top of the PDFView when the user is annotating.

This view uses it's default touchesBegan/touchesMoved/touchesEnded methods to create a bezier path following the gesture. Once the touch has ended, my view then saves it as an annotation on the pdf.

Note: you would need a way for the user to decide if they were in an annotating state.

For my main class

class MyViewController : UIViewController, PDFViewDelegate, VCDelegate {

var pdfView: PDFView?
var touchView: AnnotateView?

override func loadView() {
   touchView = AnnotateView(frame: CGRect(x: 0, y: 0, width: 375, height: 600))
   touchView?.backgroundColor = .clear
   touchView?.delegate = self
   view.addSubview(touchView!)
}

 func addAnnotation(_ annotation: PDFAnnotation) {
    print("Anotation added")
    pdfView?.document?.page(at: 0)?.addAnnotation(annotation)
}
}

My annotation view

class AnnotateView: UIView {
var path: UIBezierPath?
var delegate: VCDelegate?

override func touchesBegan(_ touches: Set, with event: UIEvent?) {
    // Initialize a new path for the user gesture
    path = UIBezierPath()
    path?.lineWidth = 4.0

    var touch: UITouch = touches.first!
    path?.move(to: touch.location(in: self))
}

override func touchesMoved(_ touches: Set, with event: UIEvent?) {

    // Add new points to the path
    let touch: UITouch = touches.first! 
    path?.addLine(to: touch.location(in: self))
    self.setNeedsDisplay()
}

override func touchesEnded(_ touches: Set, with event: UIEvent?) {

    let touch = touches.first 
    path?.addLine(to: touch!.location(in: self))
    self.setNeedsDisplay()
    let annotation = PDFAnnotation(bounds: self.bounds, forType: .ink, withProperties: nil)
    annotation.add(self.path!)
    delegate?.addAnnotation(annotation)
}

override func touchesCancelled(_ touches: Set, with event: UIEvent?) {
    self.touchesEnded(touches, with: event)
}

override func draw(_ rect: CGRect) {
    // Draw the path
    path?.stroke()
}

override init(frame: CGRect) {
    super.init(frame: frame)
    self.isMultipleTouchEnabled = false
}
}