Embed PDFViewController as a child in iOS

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//
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//  Copyright © 2021-2025 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 ChildViewControllerExample: Example {
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    override init() {
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        super.init()
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        title = "View Controller Containment"
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        contentDescription = "Shows how to embed a PDFViewController as a child view controller."
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        category = .controllerCustomization
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        priority = 30
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController? {
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        ParentViewController(document: AssetLoader.document(for: .annualReport))
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    }
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}
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private class ParentViewController: UIViewController, PDFViewControllerDelegate, UIToolbarDelegate {
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    init(document: Document?) {
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        self.document = document
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        super.init(nibName: nil, bundle: nil)
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    }
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    required init?(coder: NSCoder) {
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        fatalError("init(coder:) has not been implemented")
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    }
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    var document: Document? {
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        didSet {
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            guard oldValue !== document else { return }
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            pdfViewController.document = document
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        }
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    }
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    private lazy var pdfViewController = PDFViewController(document: document, delegate: self) { builder in
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        builder.pageTransition = .scrollContinuous
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        builder.scrollDirection = .vertical
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        builder.isShadowEnabled = false
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        builder.shouldHideNavigationBarWithUserInterface = false
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    }
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    private lazy var toolbar = UIToolbar()
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    override func viewDidLoad() {
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        super.viewDidLoad()
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        view.backgroundColor = .systemGray
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        // Set up the view hierarchy.
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        view.addSubview(toolbar)
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        addChild(pdfViewController)
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        view.addSubview(pdfViewController.view)
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        pdfViewController.didMove(toParent: self)
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        // The delegate is needed to attach the toolbar to the top of the screen.
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        // Otherwise, there will be a gap under the status bar.
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        toolbar.delegate = self
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        toolbar.items = [
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            .init(title: "Done", style: .done, target: self, action: #selector(doneBarButtonItemPressed)),
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            .init(barButtonSystemItem: .flexibleSpace, target: nil, action: nil),
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            pdfViewController.outlineButtonItem,
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            pdfViewController.annotationButtonItem,
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            pdfViewController.bookmarkButtonItem
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        ]
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        // Lay out the views using Auto Layout.
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        toolbar.translatesAutoresizingMaskIntoConstraints = false
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        pdfViewController.view.translatesAutoresizingMaskIntoConstraints = false
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        NSLayoutConstraint.activate([
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            toolbar.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
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            toolbar.leftAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leftAnchor),
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            toolbar.rightAnchor.constraint(equalTo: view.safeAreaLayoutGuide.rightAnchor),
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            pdfViewController.view.topAnchor.constraint(equalTo: toolbar.bottomAnchor, constant: 44),
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            pdfViewController.view.leftAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leftAnchor, constant: 44),
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            pdfViewController.view.rightAnchor.constraint(equalTo: view.safeAreaLayoutGuide.rightAnchor, constant: -44),
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            pdfViewController.view.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -44),
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        ])
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    }
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    override func viewWillAppear(_ animated: Bool) {
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        super.viewWillAppear(animated)
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        navigationController?.setNavigationBarHidden(true, animated: animated)
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    }
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    override func viewWillLayoutSubviews() {
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        super.viewWillLayoutSubviews()
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        // If the example was invoked from the search, hiding the navigation bar
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        // in viewWillAppear won't work. So we do it here again, just in case.
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        if navigationController?.navigationBar.isHidden ?? true { return }
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        navigationController?.setNavigationBarHidden(true, animated: false)
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    }
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    override func viewWillDisappear(_ animated: Bool) {
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        super.viewWillDisappear(animated)
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        navigationController?.setNavigationBarHidden(false, animated: animated)
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    }
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    func position(for bar: UIBarPositioning) -> UIBarPosition {
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        .topAttached
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    }
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    @objc private func doneBarButtonItemPressed(_ sender: UIBarButtonItem) {
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        navigationController?.popViewController(animated: true)
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    }
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}