How to know when PDF document is downloaded in PDFKit? - swift

Question

I'm building a really simple app, which displays PDF documents. However, how to know when PDF document is rendered?
Here's how my app looks like:
Now, I have a ProgressView which shows while the document is being downloaded. How do I hide the ProgressView when the document is downloaded and begins to render? I'm doing all of this in SwiftUI, I connected the PDFKit using UIKit in a SwiftUI app. Now, how do I. do it? I found this, but this applies only to UIKit: How to know when a PDF is rendered using PDFKit
My code:
PDFRepresentedView:
import SwiftUI
import PDFKit
struct PDFRepresentedView: UIViewRepresentable {
typealias UIViewType = PDFView
let url: URL
let singlePage: Bool
init(_ url: URL, singlePage: Bool = false) {
self.url = url
self.singlePage = singlePage
}
func makeUIView(context _: UIViewRepresentableContext<PDFRepresentedView>) -> UIViewType {
let pdfView = PDFView()
pdfView.document = PDFDocument(url: url)
pdfView.autoScales = true
if singlePage {
pdfView.displayMode = .singlePage
}
return pdfView
}
func updateUIView(_ pdfView: UIViewType, context: UIViewRepresentableContext<PDFRepresentedView>) {
pdfView.document = PDFDocument(url: url)
}
}
PDFReaderView:
import SwiftUI
struct PDFReaderView: View {
var url: URL
var body: some View {
ProgressView("pdf.downloading")
}
}
struct PDFReaderView_Previews: PreviewProvider {
static var previews: some View {
PDFReaderView(url: URL(string: "https://isap.sejm.gov.pl/isap.nsf/download.xsp/WDU19600300168/U/D19600168Lj.pdf")!)
}
}
HomeView:
import SwiftUI
struct HomeView: View {
#AppStorage("needsAppOnboarding") private var needsAppOnboarding: Bool = true
var body: some View {
NavigationView {
List(deeds) { deed in
NavigationLink(destination: PDFReaderView(url: deed.url)) {
Text(deed.name)
}
}
.navigationTitle("title")
}
.sheet(isPresented: $needsAppOnboarding) {
OnboardingView()
}
}
}
struct HomeView_Previews: PreviewProvider {
static var previews: some View {
HomeView()
}
}

Answer 1

Seems like a better option than letting PDFDocument do the loading from the URL would be to load the data yourself. Then, you can respond appropriately to errors, etc.
import PDFKit
import SwiftUI
import Combine
class DataLoader : ObservableObject {
#Published var data : Data?
var cancellable : AnyCancellable?
func loadUrl(url: URL) {
cancellable = URLSession.shared.dataTaskPublisher(for: url)
.map { $0.data }
.receive(on: RunLoop.main)
.sink(receiveCompletion: { (completion) in
switch completion {
case .failure(let failureType):
print(failureType)
//handle potential errors here
case .finished:
break
}
}, receiveValue: { (data) in
self.data = data
})
}
}
struct ContentView : View {
#StateObject private var dataLoader = DataLoader()
var body: some View {
VStack {
if let data = dataLoader.data {
PDFRepresentedView(data: data)
} else {
Text("Loading")
}
}.onAppear {
dataLoader.loadUrl(url: URL(string: "https://isap.sejm.gov.pl/isap.nsf/download.xsp/WDU19600300168/U/D19600168Lj.pdf")!)
}
}
}
struct PDFRepresentedView: UIViewRepresentable {
typealias UIViewType = PDFView
let data: Data
let singlePage: Bool = false
func makeUIView(context _: UIViewRepresentableContext<PDFRepresentedView>) -> UIViewType {
let pdfView = PDFView()
pdfView.document = PDFDocument(data: data)
pdfView.autoScales = true
if singlePage {
pdfView.displayMode = .singlePage
}
return pdfView
}
func updateUIView(_ pdfView: UIViewType, context: UIViewRepresentableContext<PDFRepresentedView>) {
pdfView.document = PDFDocument(data: data)
}
}
In this example, DataLoader is responsible for getting the Data from the URL. Note the comment I've left in about where you might respond to errors.
Back in the main view, "Loading" is displayed unless there's Data available, in which case PDFRepresentedView is now shown, which now takes a Data object instead of a URL.