Show or hide PDF annotations using Swift for iOS

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//
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//  Copyright © 2020-2026 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 ToggleAnnotationVisibilityExample: Example {
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    override init() {
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        super.init()
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        title = "Toggle Annotation Visibility"
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        contentDescription = "Allow users to hide or show annotations."
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        category = .annotations
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        priority = 10
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
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        let document = AssetLoader.writableDocument(for: .welcome, overrideIfExists: false)
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        // Clear cache before presenting the view controller so that pages are
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        // re-rendered with annotations visible by default, in case the last
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        // cache has annotations hidden.
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        PSPDFKit.SDK.shared.cache.remove(for: document)
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        // Due to the limitation of this example, thumbnail bar won't be updated
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        // when hiding or showing annotations. So let's disable it.
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        let controller = ToggleAnnotationVisibilityViewController(document: document) { builder in
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            builder.thumbnailBarMode = .none
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        }
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        // Go directly to the page with annotations.
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        controller.pageIndex = 15
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        return controller
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    }
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}
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private class ToggleAnnotationVisibilityViewController: PDFViewController {
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    override func commonInit(with document: Document?, configuration: PDFConfiguration) {
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        super.commonInit(with: document, configuration: configuration)
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        let toggleAnnotationVisibilityBarButtonItem = UIBarButtonItem(image: UIImage(namedInCatalog: "hide"), style: .plain, target: self, action: #selector(didTapToggleAnnotationVisibilityBarButtonItem))
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        toggleAnnotationVisibilityBarButtonItem.title = "hide"
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        navigationItem.rightBarButtonItems = [toggleAnnotationVisibilityBarButtonItem]
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    }
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    @objc func didTapToggleAnnotationVisibilityBarButtonItem(_ sender: UIBarButtonItem) {
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        // Let link annotations be always visible.
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        if sender.title == "hide" {
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            setVisibleAnnotationTypes(.link)
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            sender.title = "show"
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            sender.image = UIImage(namedInCatalog: "show")
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        } else {
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            setVisibleAnnotationTypes(.all)
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            sender.title = "hide"
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            sender.image = UIImage(namedInCatalog: "hide")
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        }
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    }
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    // MARK: Private
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    private func setVisibleAnnotationTypes(_ types: Annotation.Kind) {
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        // Update the render types.
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        document?.renderAnnotationTypes = types
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        // Clear the cache so that pages are re-rendered once updated.
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        PSPDFKit.SDK.shared.cache.remove(for: document)
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        for pageView in visiblePageViews {
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            pageView.updateAnnotationViews(animated: false)
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            pageView.update()
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        }
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    }
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}