Swift UI and PDFKit - How do I update my page programmatically? - swiftui

Question

I want to update the view when the State of currentpage changes by a button.
In console the tap make current page increase accordingly.
I tried with gotoNextPage() (SOLUTION 2)and it is not working
and also tried with go to method.(SOLUTION 1)
Non of them are updating even if printed values seems to be ok.
PDFVIEW CurrentPage value is:Optional(<PDFPage: 0x281917b60> page index 203)
Any solution, please?
#State var pdfName: String
#State var start: Int
PDFKitView(url: Bundle.main.url(forResource: pdfName, withExtension: "pdf")!, currentPage: start)
import SwiftUI
import PDFKit
struct PDFKitView: View {
var url: URL
var currentPage: Int
var body: some View {
PDFKitRepresentedView(url, currentPage)
}
}
struct PDFKitRepresentedView: UIViewRepresentable {
let url: URL
let currentPage: Int
let pdfView = PDFView()
init(_ url: URL, _ currentPage: Int) {
self.url = url
self.currentPage = currentPage
}
func makeUIView(context: UIViewRepresentableContext<PDFKitRepresentedView>) -> PDFKitRepresentedView.UIViewType {
print("PDFVIEW IS CREATED")
pdfView.document = PDFDocument(url: self.url)
pdfView.displayMode = .singlePage
pdfView.displayDirection = .horizontal
pdfView.autoScales = true
pdfView.usePageViewController(true)
pdfView.go(to: pdfView.document!.page(at: currentPage)!)
let total = pdfView.document?.pageCount
print("Total pages: \(total ?? 0)")
return pdfView
}
func updateUIView(_ uiView: UIView, context: UIViewRepresentableContext<PDFKitRepresentedView>) {
// Update the view.
//THIS IS PRINTED IN CONSOLE EVERY TIME
print("PDFVIEW IS UPDATED")
print("CurrentPage value is:\(currentPage)")
//SOLUTION TRIED 1. SAME CODE WORKS ON makeUIView: I can see the pdf, scroll it and zoom. Also let it start at any page I want to. But not here.
print("PDFVIEW IS UPDATED")
print("CurrentPage value is:\(currentPage)")
//SOLUTION 1
pdfView.document = PDFDocument(url: self.url)
pdfView.displayMode = .singlePage
pdfView.displayDirection = .horizontal
pdfView.autoScales = true
pdfView.usePageViewController(true)
pdfView.go(to: pdfView.document!.page(at: currentPage)!)
print("PDFVIEW CurrentPage value is:\(pdfView.currentPage)")
/*
PDFVIEW IS UPDATED
CurrentPage value is:203
PDFVIEW CurrentPage value is:Optional(<PDFPage: 0x281917b60> page index 203)
*/
//SOLUTION TRIED 2
//goToNextPage()
}
func goToNextPage(){
pdfView.goToNextPage(nil)
}
}

Answer 1

The source of truth should be somewhere outside and injected by binding or other observable type inside.
Here is simplified fixed variant. Tested with Xcode 13.4 / iOS 15.5
Main part:
func makeUIView(context: Context) -> UIView {
guard let document = PDFDocument(url: self.url) else { return UIView() }
let pdfView = PDFView()
print("PDFVIEW IS CREATED")
pdfView.document = document
pdfView.displayMode = .singlePage
pdfView.displayDirection = .horizontal
pdfView.autoScales = true
pdfView.usePageViewController(true)
DispatchQueue.main.async {
self.total = document.pageCount
print("Total pages: \(total)")
}
return pdfView
}
func updateUIView(_ uiView: UIView, context: Context) {
guard let pdfView = uiView as? PDFView else { return }
if currentPage < total {
pdfView.go(to: pdfView.document!.page(at: currentPage)!)
}
}
Note: handling PDFView delegate navigation by swipe to pass back in binding is on you.
Complete test module is here