Show Multiple PDFs with Tabbed UI using Swift for iOS

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//
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//  Copyright © 2017-2025 PSPDFKit GmbH. All rights reserved.
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//
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//  The Nutrient sample applications are licensed with a modified BSD license.
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//  Please see License for details. This notice may not be removed from this file.
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//
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import PSPDFKit
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import PSPDFKitUI
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class TabbedBarExample: Example {
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    override init() {
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        super.init()
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        title = "Tabbed Bar"
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        contentDescription = "Opens multiple documents in a tabbed interface."
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        category = .top
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        targetDevice = [.vision, .phone, .pad]
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        priority = 3
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController? {
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        return TabbedExampleViewController()
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    }
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}
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class TabbedExampleViewController: PDFTabbedViewController, PDFTabbedViewControllerDelegate {
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    var clearTabsButtonItem = UIBarButtonItem()
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    override func commonInit(withPDFController pdfController: PDFViewController?) {
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        super.commonInit(withPDFController: pdfController)
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        // In case pdfController was nil and commonInitWithPDFController created it.
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        let controller = self.pdfController
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        delegate = self
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        navigationItem.leftItemsSupplementBackButton = true
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        allowDraggingTabsToExternalTabbedBar = true
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        allowDroppingTabsFromExternalTabbedBar = true
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        let samplesURL = FileHelper.copySamplesToDocumentDirectory(overwrite: true)
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        documentPickerController = PDFDocumentPickerController(directory: samplesURL.path, includeSubdirectories: true, library: SDK.shared.library)
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        clearTabsButtonItem = UIBarButtonItem(image: SDK.imageNamed("trash"), style: .plain, target: self, action: #selector(clearTabsButtonPressed(sender:)))
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        controller.barButtonItemsAlwaysEnabled = [clearTabsButtonItem]
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        controller.navigationItem.setLeftBarButtonItems([clearTabsButtonItem], for: .document, animated: false)
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        controller.setUpdateSettingsForBoundsChange { [weak self] _ in
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            self?.updateBarButtonItems()
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        }
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        // Show some documents initially. You can open more using the + button at the left end of the tabbed bar.
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        documents = [AssetName.welcome, AssetName.psychologyResearch, AssetName.cosmicContextForLife].map {
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            Document(url: samplesURL.appendingPathComponent($0.rawValue))
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        }
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        NotificationCenter.default.addObserver(self, selector: #selector(documentOpenedInNewSceneNotification(_:)), name: .PSCDocumentOpenedInNewScene, object: nil)
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    }
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    override func viewWillAppear(_ animated: Bool) {
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        super.viewWillAppear(animated)
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        updateBarButtonItems()
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    }
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    override func addDocument(_ document: Document, makeVisible shouldMakeDocumentVisible: Bool, animated: Bool) {
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        super.addDocument(document, makeVisible: shouldMakeDocumentVisible, animated: animated)
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        document.userActivity = userActivity(for: document)
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    }
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    override var documents: [Document] {
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        didSet {
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            for document in documents {
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                document.userActivity = userActivity(for: document)
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            }
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        }
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    }
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    private func userActivity(for document: Document) -> NSUserActivity? {
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        guard let fileURL = document.fileURL else { return nil }
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        return NSUserActivity.openDocumentActivity(forFileURL: fileURL)
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    }
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    // MARK: - Private
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    @objc func clearTabsButtonPressed(sender: UIBarButtonItem) {
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        let sheetController = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)
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        sheetController.addAction(UIAlertAction(title: "Cancel", style: .cancel))
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        sheetController.addAction(UIAlertAction(title: "Close All Tabs", style: UIAlertAction.Style.destructive, handler: { [weak self] _ in
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            self?.documents = []
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        }))
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        let popoverPresentation = sheetController.popoverPresentationController
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        popoverPresentation?.barButtonItem = sender
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        present(sheetController, animated: true)
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    }
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    func updateBarButtonItems() {
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        let controller = self.pdfController
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        var items = [controller.thumbnailsButtonItem, controller.activityButtonItem, controller.annotationButtonItem, controller.contentEditingButtonItem]
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        // Add more items if we have space available
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        if traitCollection.horizontalSizeClass == .regular {
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            items.insert(controller.outlineButtonItem, at: 2)
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            items.insert(controller.searchButtonItem, at: 2)
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        }
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        controller.navigationItem.setRightBarButtonItems(items, for: .document, animated: false)
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    }
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    func updateToolbarItems() {
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        clearTabsButtonItem.isEnabled = !documents.isEmpty
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    }
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    internal func multiPDFController(_ multiPDFController: MultiDocumentViewController, didChange oldDocuments: [Document]) {
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        updateToolbarItems()
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    }
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    @objc func documentOpenedInNewSceneNotification(_ notification: Notification) {
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        guard let url = notification.userInfo?["documentURL"] as? URL else { return }
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        for document in self.documents where url.resolvingSymlinksInPath() == document.fileURL?.resolvingSymlinksInPath() {
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            self.removeDocument(document, animated: true)
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        }
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    }
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}