Embed a SwiftUI View inside a Page View on iOS

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//
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//  Copyright © 2020-2025 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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import SwiftUI
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class SwiftUIOnPageViewExample: Example, PDFViewControllerDelegate {
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    override init() {
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        super.init()
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        title = "Using SwiftUI on a page"
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        contentDescription = "Shows how to add a SwiftUI view embedded on a page view."
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        category = .swiftUI
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        priority = 20
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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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        let controller = PDFViewController(document: document) { builder in
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            builder.overrideClass(PDFPageView.self, with: ButtonPageView.self)
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        }
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        controller.delegate = self
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        return controller
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    }
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    func pdfViewController(_ pdfController: PDFViewController, didConfigurePageView pageView: PDFPageView, forPageAt pageIndex: Int) {
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        guard let buttonPageView = pageView as? ButtonPageView else { return }
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        let hostingController = UIHostingController(rootView: PageButton(pageIndex: buttonPageView.pageIndex))
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        hostingController.view.backgroundColor = UIColor.clear
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        hostingController.view.translatesAutoresizingMaskIntoConstraints = false
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        pdfController.documentViewController?.addChild(hostingController)
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        buttonPageView.addSubview(hostingController.view)
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        hostingController.didMove(toParent: pdfController.documentViewController)
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        NSLayoutConstraint.activate([
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            hostingController.view.centerXAnchor.constraint(equalTo: buttonPageView.centerXAnchor),
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            hostingController.view.centerYAnchor.constraint(equalTo: buttonPageView.centerYAnchor),
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        ])
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        buttonPageView.hostingController = hostingController
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    }
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}
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private class ButtonPageView: PDFPageView {
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    fileprivate var hostingController: UIHostingController<PageButton>?
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    override func prepareForReuse() {
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        super.prepareForReuse()
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        hostingController?.willMove(toParent: nil)
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        hostingController?.view.removeFromSuperview()
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        hostingController?.removeFromParent()
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    }
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}
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private struct PageButton: View {
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    @State var showAlert = false
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    let pageIndex: PageIndex
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    var body: some View {
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        Button(action: {
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            self.showAlert = true
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        }, label: {
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            Text("Page \(pageIndex + 1)")
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        })
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        .font(.headline)
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        .padding()
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        .background(Color.accentColor)
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        .cornerRadius(10)
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        .foregroundColor(.white)
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        .alert(isPresented: $showAlert) {
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            Alert(title: Text("Tapped on page \(pageIndex + 1)"))
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        }
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        .edgesIgnoringSafeArea(.all)
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    }
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}