Presenting UIDocumentInteractionController with UIViewControllerRepresentable in SwiftUI - ios

Question

I'm creating a new iOS app using SwiftUI where ever possible. However, I want to be able to generate a PDF with some data.
In a similar project without swiftUI I can do this
let docController = UIDocumentInteractionController.init(url: "PATH_TO_FILE")
docController.delegate = self
self.dismiss(animated: false, completion: {
docController.presentPreview(animated: true)
})
and as long as somewhere else in the view controller I have this:
func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController {
return self
}
I'm good to go.
What I can't work out is how to apply this to a UIViewControllerRepresentable and have it working in SwiftUI. Should my UIViewControllerRepresentable be aiming to be a UIViewController? How do I then set the delegate and presentPreview? Will this overlay any view and display full screen over my SwiftUI app as it does for my standard iOS app?
Thanks

Answer 1

Here is possible approach to integrate UIDocumentInteractionController for usage from SwiftUI view.
Full-module code. Tested with Xcode 11.2 / iOS 13.2
import SwiftUI
import UIKit
struct DocumentPreview: UIViewControllerRepresentable {
private var isActive: Binding<Bool>
private let viewController = UIViewController()
private let docController: UIDocumentInteractionController
init(_ isActive: Binding<Bool>, url: URL) {
self.isActive = isActive
self.docController = UIDocumentInteractionController(url: url)
}
func makeUIViewController(context: UIViewControllerRepresentableContext<DocumentPreview>) -> UIViewController {
return viewController
}
func updateUIViewController(_ uiViewController: UIViewController, context: UIViewControllerRepresentableContext<DocumentPreview>) {
if self.isActive.wrappedValue && docController.delegate == nil { // to not show twice
docController.delegate = context.coordinator
self.docController.presentPreview(animated: true)
}
}
func makeCoordinator() -> Coordintor {
return Coordintor(owner: self)
}
final class Coordintor: NSObject, UIDocumentInteractionControllerDelegate { // works as delegate
let owner: DocumentPreview
init(owner: DocumentPreview) {
self.owner = owner
}
func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController {
return owner.viewController
}
func documentInteractionControllerDidEndPreview(_ controller: UIDocumentInteractionController) {
controller.delegate = nil // done, so unlink self
owner.isActive.wrappedValue = false // notify external about done
}
}
}
// Demo of possible usage
struct DemoPDFPreview: View {
#State private var showPreview = false // state activating preview
var body: some View {
VStack {
Button("Show Preview") { self.showPreview = true }
.background(DocumentPreview($showPreview, // no matter where it is, because no content
url: Bundle.main.url(forResource: "example", withExtension: "pdf")!))
}
}
}
struct DemoPDFPreview_Previews: PreviewProvider {
static var previews: some View {
DemoPDFPreview()
}
}

Answer 2

I ended up doing something like the following as I wasn't able to get this working reliably with UIViewControllerRepresentable and the above answer. You might need to edit / extend this for your usecase.
class DocumentController: NSObject, ObservableObject, UIDocumentInteractionControllerDelegate {
let controller = UIDocumentInteractionController()
func presentDocument(url: URL) {
controller.delegate = self
controller.url = url
controller.presentPreview(animated: true)
}
func documentInteractionControllerViewControllerForPreview(_: UIDocumentInteractionController) -> UIViewController {
return UIApplication.shared.windows.first!.rootViewController!
}
}
Usage:
struct DocumentView: View {
#StateObject var documentController = DocumentController()
var body: some View {
Button(action: {
documentController.presentDocument(url: ...)
}, label: {
Text("Show Doc")
})
}
}

Answer 3

Using QLPreviewController
I know the question is about UIDocumentInteractionController, but if you want to present a PDF file (for example), you can use a QLPreviewController.
Local file
Presenting a local file:
import SwiftUI
struct DocView: View {
#State private var buttonPressed: Bool = false
var body: some View {
Button {
buttonPressed = true
} label: {
Text("Show PDF file")
}
.sheet(isPresented: $buttonPressed) {
let localURL = Bundle.main.url(forResource: "Example", withExtension: "pdf")!
PreviewController(url: localURL)
}
}
}
Remote file
Please see this gist if you need to present a remote file.
PreviewController
The UIViewControllerRepresentable for QLPreviewController.
import QuickLook
import SwiftUI
struct PreviewController: UIViewControllerRepresentable {
#Environment(\.dismiss) private var dismiss
let url: URL
func makeUIViewController(context: Context) -> UINavigationController {
let controller = QLPreviewController()
controller.dataSource = context.coordinator
controller.navigationItem.leftBarButtonItem = UIBarButtonItem(
barButtonSystemItem: .done, target: context.coordinator,
action: #selector(context.coordinator.dismiss)
)
let navigationController = UINavigationController(rootViewController: controller)
return navigationController
}
func updateUIViewController(_ uiViewController: UINavigationController, context: Context) {}
func makeCoordinator() -> Coordinator {
return Coordinator(parent: self)
}
class Coordinator: QLPreviewControllerDataSource {
let parent: PreviewController
init(parent: PreviewController) {
self.parent = parent
}
func numberOfPreviewItems(in controller: QLPreviewController) -> Int {
return 1
}
func previewController(
_ controller: QLPreviewController,
previewItemAt index: Int
) -> QLPreviewItem {
return parent.url as NSURL
}
#objc func dismiss() {
parent.dismiss()
}
}
}