PDFView in swift

In the article, I will discuss about the PDFKit framework and how we use PDFView in our swift project.

The PDFKit is a framework available in AppKit since iOS 11.0 and macOS 10.4. Please click here to read more about PDFKit.

PDFView is mainly used to show the pdf file in our application and also it allows users to set zoom level, select content, navigate through a document, and copy the textual content to the Pasteboard, and also keeps track of page history.

Declaration

iOS, Mac Catalyst

class PDFView : UIView

1	class PDFView : UIView

macOS

class PDFView : NSView

1	class PDFView : NSView

Getting Started

Swift version: 5
iOS version: 13
Xcode: 11.3

First Create a project from Xcode.

File ▸ New ▸ Project…. Choose the iOS ▸ Application ▸ Single View App template and create a new project.

Then, we will create an object of PDFView and we will add this view inside the super view.

let pdfView = PDFView(frame: self.view.bounds)
pdfView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
self.view.addSubview(pdfView)

let pdfView = PDFView(frame: self.view.bounds)

pdfView.autoresizingMask = [.flexibleWidth, .flexibleHeight]

self.view.addSubview(pdfView)

Now we load a pdf file from the app bundle.

 let fileURL = Bundle.main.url(forResource: "Demo", withExtension: "pdf")
 pdfView.document = PDFDocument(url: fileURL!)

1 2	let fileURL = Bundle.main.url(forResource: "Demo", withExtension: "pdf") pdfView.document = PDFDocument(url: fileURL!)

We can Fit content in the pdfview set autoScales true

pdfView.autoScales = true

1	pdfView.autoScales = true

Now run code and it will display Demo.pdf file in our app.

Now we will add a watermark in the PDFView.

First we have to initializes a PDFDocument instance and sets its delegate to self.

let document = PDFDocument(url: fileURL!)
document?.delegate = self
pdfView.document = document

let document = PDFDocument(url: fileURL!)

document?.delegate = self

pdfView.document = document

Now, the delegate, of type PDFDocumentDelegate, implements a classForPage() method.

func classForPage() -> AnyClass {
    return WatermarkPage.self
}

func classForPage() -> AnyClass {

return WatermarkPage.self

}

Now, implement WatermarkPage class and draw the watermark.

class WatermarkPage : PDFPage{
    override func draw(with box: PDFDisplayBox, to context: CGContext) {
        
        // Draw original content
        super.draw(with: box, to: context)
        
        // Draw rotated overlay string
        UIGraphicsPushContext(context)
        context.saveGState()
        
        let pageBounds = self.bounds(for: box)
        context.translateBy(x: 0.0, y: pageBounds.size.height)
        context.scaleBy(x: 1.0, y: -1.0)
        context.rotate(by: CGFloat.pi / 4.0)
        
        let string: NSString = "U s e r   3 1 4 1 5 9"
        let attributes: [NSAttributedString.Key: Any] = [
            NSAttributedString.Key.foregroundColor:  colorLiteral(red: 0.4980392157, green: 0.4980392157, blue: 0.4980392157, alpha: 0.5),
            NSAttributedString.Key.font: UIFont.boldSystemFont(ofSize: 64)
        ]
        
        string.draw(at: CGPoint(x: 250, y: 40), withAttributes: attributes)
        
        context.restoreGState()
        UIGraphicsPopContext()
        
    }
}

class WatermarkPage : PDFPage{

override func draw(with box: PDFDisplayBox, to context: CGContext) {

// Draw original content

super.draw(with: box, to: context)

// Draw rotated overlay string

UIGraphicsPushContext(context)

context.saveGState()

let pageBounds = self.bounds(for: box)

context.translateBy(x: 0.0, y: pageBounds.size.height)

context.scaleBy(x: 1.0, y: -1.0)

context.rotate(by: CGFloat.pi / 4.0)

let string: NSString = "U s e r 3 1 4 1 5 9"

let attributes: [NSAttributedString.Key: Any] = [

NSAttributedString.Key.foregroundColor: colorLiteral(red: 0.4980392157, green: 0.4980392157, blue: 0.4980392157, alpha: 0.5),

NSAttributedString.Key.font: UIFont.boldSystemFont(ofSize: 64)

]

string.draw(at: CGPoint(x: 250, y: 40), withAttributes: attributes)

context.restoreGState()

UIGraphicsPopContext()

}

I hope this article helps you to display the pdf file in the project.

Debabrata Roy 1 November 2020

. . .

3 comments

David Feb 26, 2021 at 9:42 am

How do you go about adding a button or some sort of way to exit this PDF subview?

Debabrata Roy (Moderator) Oct 12, 2021 at 8:15 pm
Use a custom class and drawPagePost method.
Exemple:
class customPDF : PDFView {
public override func drawPagePost(_ page: PDFPage, to context: CGContext) {
let subview = UIView()
self.documentView?.addSubview(subview)
}
}

Reply

Tobias Aug 2, 2022 at 10:58 am

How would you inject e.g. a userName from an external struct or class into the WatermarkPage class as the string to be used, when func classForPage() only returns the type WatermarkPage?

Many thanks for your help & BR
Tobias

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