Save Reading Position in PDF using Swift for iOS

1
//
2
//  Copyright © 2019-2025 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
        title = "Document View State Restoration"
19
        contentDescription = "Restores document to a previously stored reading position."
20
        category = .controllerCustomization
21
    }
22

23
    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
24
           let document = AssetLoader.writableDocument(for: .welcome, overrideIfExists: false)
25

26
           let controller = PDFViewController(document: document)
27
           controller.delegate = self
28

29
           // Apply the saved view state.
30
           if let data = UserDefaults.standard.object(forKey: viewStateKey) as? Data,
31
            let unarchivedObject = try? NSKeyedUnarchiver.unarchivedObject(ofClasses: [PDFViewState.self], from: data),
32
            let state = unarchivedObject as? PDFViewState {
33
               controller.applyViewState(state, animateIfPossible: true)
34
           }
35

36
           return controller
37
    }
38

39
    // MARK: - PDFViewControllerDelegate
40
    func pdfViewControllerWillDismiss(_ pdfController: PDFViewController) {
41
        // Persist the current view state.
42
        guard let viewState = pdfController.viewState,
43
            let data = try? NSKeyedArchiver.archivedData(withRootObject: viewState, requiringSecureCoding: true) else {
44
            print("Error archiving view state.")
45
            return
46
        }
47

48
        UserDefaults.standard.set(data, forKey: viewStateKey)
49
    }
50
}