Save reading position in PDF using Swift for iOS

1
//
2
//  Copyright © 2019-2026 PSPDFKit GmbH. All rights reserved.
3
//
4
//  The Nutrient sample applications are licensed with a modified BSD license.
5
//  Please see License for details. This notice may not be removed from this file.
6
//
7

8
import PSPDFKit
9
import PSPDFKitUI
10

11
class DocumentViewStateRestoration: Example, PDFViewControllerDelegate {
12

13
    let viewStateKey = "viewStateKey"
14

15
    override init() {
16
        super.init()
17

18
        contentDescription = "Restores document to a previously stored reading position."
19
        category = .controllerCustomization
20
    }
21

22
    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
23
           let document = AssetLoader.writableDocument(for: .welcome, overrideIfExists: false)
24

25
           let controller = PDFViewController(document: document)
26
           controller.delegate = self
27

28
           // Apply the saved view state.
29
           if let data = UserDefaults.standard.object(forKey: viewStateKey) as? Data,
30
            let unarchivedObject = try? NSKeyedUnarchiver.unarchivedObject(ofClasses: [PDFViewState.self], from: data),
31
            let state = unarchivedObject as? PDFViewState {
32
               controller.applyViewState(state, animateIfPossible: true)
33
           }
34

35
           return controller
36
    }
37

38
    // MARK: - PDFViewControllerDelegate
39
    func pdfViewControllerWillDismiss(_ pdfController: PDFViewController) {
40
        // Persist the current view state.
41
        guard let viewState = pdfController.viewState,
42
            let data = try? NSKeyedArchiver.archivedData(withRootObject: viewState, requiringSecureCoding: true) else {
43
            print("Error archiving view state.")
44
            return
45
        }
46

47
        UserDefaults.standard.set(data, forKey: viewStateKey)
48
    }
49
}