如果Firebase具有pdf属性，我想在我的IOS应用程序中的pdfView中显示它

Question

我正在尝试创建一个应用程序，其中包含一个公告列表，连接到Firebase服务器进行测试，如果Firebase具有pdf属性，我想在应用程序中显示它。

以下代码如下：

import UIKit
import FirebaseDatabaseUI
import Firebase
import Down
import FontAwesomeIconFactory
import PDFKit


extension AnnouncementDetailViewController: PDFViewDelegate {
    func pdfViewWillClick(onLink sender: PDFView, with url: URL){
        print(url)
    }
}

class AnnouncementDetailViewController: UIViewController {

    @IBOutlet var authorLabel: UILabel!
    @IBOutlet var titleLabel: UILabel!
    @IBOutlet var authorImage: UIImageView!
    var announcementKey = ""
    let announcement: Announcement = Announcement()
    lazy var ref: DatabaseReference = Database.database().reference()
    var announcementRef: DatabaseReference!
    var refHandle: DatabaseHandle?
    var contentView: DownView?
    var pdfView: PDFView!

    override func viewDidLoad() {
        super.viewDidLoad()

        initialiseContentView()
        initialseDatabaseChild()
        initialiseNavbarTitle()

        //Method calls for Pdf
        configureUI()
        loadPDF()
        playWithPDF()

    }


    private func configureUI(){
        pdfView = PDFView ()
        pdfView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(pdfView)

        pdfView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        pdfView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        pdfView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        pdfView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true

        pdfView.delegate = self
    }

    private func addObservers(){
        NotificationCenter.default.addObserver(self, selector: #selector(handlePageChange(notification:)), name: Notification.Name.PDFViewPageChanged, object: nil)
    }

    @objc private func handlePageChange(notification: Notification){
        print("Current page is changed")
    }

    private func loadPDF() {
        guard
        let url = URL(string:"http://www.pdf995.com/samples/pdf.pdf"),
            let document = PDFDocument(url: url)
            else { return }

        if document.isLocked && document.unlock(withPassword: "test"){
        pdfView.document = document
        } else {
            print("We have a problem")
        }
    }

    private func playWithPDF(){
        pdfView.displayMode = .singlePageContinuous
        pdfView.autoScales = true
    }



    private func initialiseNavbarTitle() {
        self.navigationItem.title = "Announcement Detail"
    }
    private func initialseDatabaseChild() {
        announcementRef = ref.child("announcements").child(announcementKey)
    }
    private func generateDownViewHeight() -> CGFloat {
        return UIScreen.main.bounds.height - authorLabel.frame.height - authorImage.frame.height - (navigationController?.navigationBar.frame.height ?? 0) - view.safeAreaInsets.top - 70
    }
    private func initialiseContentView() {
        guard let contentView = try? DownView(frame: CGRect(x: 0, y: 0, width: 0, height: 0), markdownString: "") else { return }
        view.addSubview(contentView)
        contentView.scrollView.bounces = false
        contentView.translatesAutoresizingMaskIntoConstraints = false
        contentView.topAnchor.constraint(equalTo: titleLabel.bottomAnchor, constant: 5).isActive = true
        contentView.heightAnchor.constraint(equalToConstant: generateDownViewHeight()).isActive = true
        contentView.widthAnchor.constraint(equalToConstant: UIScreen.main.bounds.width).isActive = true
        self.contentView = contentView
    }

    @objc override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        refHandle = announcementRef.observe(DataEventType.value, with: { (snapshot) in
            let announcementDict = snapshot.value as? [String : AnyObject] ?? [:]
            self.announcement.setValuesForKeys(announcementDict)
            do {
                try self.contentView?.update(markdownString: self.announcement.content)
                let factory = FontAwesomeIconFactory.button()
                self.authorImage.image = factory.createImage(NIKFontAwesomeIcon.male)
                self.authorLabel.text = self.announcement.author
                self.titleLabel.text = self.announcement.title
            }
            catch {
            }
        })
    }