使用 pdfkit 显示 pdf

using pdfkit to display pdf

我正在尝试加载存储在我的应用程序中的 pdf,这是我拥有的代码

import UIKit
import PDFKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let pdfView = PDFView(frame: UIScreen.main.bounds)
        let url = Bundle.main.url(forResource: "example", withExtension: "pdf")
        pdfView.document = PDFDocument(url: url!)
        self.view.addSubview(pdfView)
    }

When I am running in simulator, I am getting the error that fatal error: unexpectedly found nil while unwrapping an Optional value in the debug are it is showing that url is nil .Any idea how to resolve it? I am running swift 4 and iOS 11 as target

请单击文件检查器中目标成员资格下的复选框。