PDFViewer SWIFT 4 Xcode 10.3

这是我的代码。我有一个文件“ dreamGirls.pdf”

import UIKit
import PDFKit

var pdfView : PDFView!

    func createPDFViewer() {
        let path = Bundle.main.path(forResource: "dreamGirls", ofType: "pdf")
        let url = URL(fileURLWithPath: path!)
        let pdfDocument = PDFDocument(url:url)

        self.pdfView.document = pdfDocument
        self.pdfView.autoScales = true
        self.pdfView.displayMode = .singlePageContinuous
        self.pdfView.displayDirection = .vertical

        let width = self.view.frame.width
        let height = self.view.frame.height - 100
        self.pdfView.frame = CGRect(x: 0, y: 100, width: width, height: height)
        self.pdfView.backgroundColor = .red
        self.view.addSubview(self.pdfView)
    }

我还尝试了以下方法：

func createPDFViewer() {

    let fileToShow = Bundle.main.url(forResource: "dreamGirls", withExtension: "pdf")
    let documentToShow = PDFDocument(url: fileToShow!)

    self.pdfView.document = documentToShow
    self.pdfView.autoScales = true
    self.pdfView.displayMode = .singlePageContinuous
    self.pdfView.displayDirection = .vertical

    let width = self.view.frame.width
    let height = self.view.frame.height - 100
    self.pdfView.frame = CGRect(x: 0, y: 100, width: width, height: height)
    self.pdfView.backgroundColor = .red
    self.view.addSubview(self.pdfView)
}

错误输出：致命错误：意外地发现nil，同时隐式展开一个可选值

pdfView PDFView？无

我也尝试过这个，并且得到了同样的错误：

import UIKit
import PDFKit

class ViewController: UIViewController {

    var pdfView : PDFView?

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        let fileToShow = Bundle.main.url(forResource: "dreamGirls", withExtension: "pdf")
        let documentToShow = PDFDocument(url: fileToShow!)

        self.pdfView!.document = documentToShow!
        self.pdfView!.autoScales = true
        self.pdfView!.displayMode = .singlePageContinuous
        self.pdfView!.displayDirection = .vertical

        let width = self.view.frame.width
        let height = self.view.frame.height - 100
        self.pdfView!.frame = CGRect(x: 0, y: 100, width: width, height: height)
        self.pdfView!.backgroundColor = .red
        self.view.addSubview(self.pdfView!)


    }


}

self pdfViewerTest.ViewController 0x00007fe538520580 UIKit.UIViewController UIViewController
pdfView PDFView吗？否无fileToShow URL？“文件：///Users/nacly/Library/Developer/CoreSimulator/Devices/C92B8B59-90C5-4509-A848-99D0B39A4469/data/Containers/Bundle/Application/7D0B63DF-F265-48DB-8887-D0563FD45FDA/pdfViewerTest.app/ dreamGirls.pdf“某些_url NSURL” file：/// Users / nacly / Library / Developer / CoreSimulator / Devices / C92B8B59-90C5-4509-A848-99D0B39A4469 / data / Containers / Bundle / Application / 7D0B63DF-F265-48DB-8887 -D0563FD45FDA / pdfViewerTest.app / dreamGirls.pdf“ 0x0000600002638120 documentToShow PDFDocument？0x00006000000301d0 ObjectiveC.NSObject NSObject
宽度CGFloat高度CGFloat

如果未初始化PDFView，我还尝试了以下操作：

import UIKit
import PDFKit

class ViewController: UIViewController {

    var pdfView : PDFView?

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        self.pdfView = PDFView()
        let fileToShow = Bundle.main.url(forResource: "dreamGirls", withExtension: "pdf")
        let documentToShow = PDFDocument(url: fileToShow!)

        self.pdfView!.document = documentToShow!
        self.pdfView!.autoScales = true
        self.pdfView!.displayMode = .singlePageContinuous
        self.pdfView!.displayDirection = .vertical

        let width = self.view.frame.width
        let height = self.view.frame.height - 100
        self.pdfView!.frame = CGRect(x: 0, y: 100, width: width, height: height)
        self.pdfView!.backgroundColor = .red
        self.view.addSubview(self.pdfView!)


    }

它返回以下错误：

pdfViewerTest [16863：1994476] *由于未捕获的异常'CALayerInvalidGeometry'而终止应用程序，原因：'CALayer位置包含NaN：[nan nan]'*第一个抛出调用堆栈：