如何解决PDFView和SCrollView之间的手势冲突[Swift5，iOS 14]

问题描述

我正在创建iPad的PDF查看器，用户可以通过该浏览器水平滚动来阅读PDF。

我创建了以下代码，以实现通过手势进行页面更改的单页面视图（同时咨询How to create a single page vertical scrolling PDFView in Swift和其他地方）。

尽管这种方法在大多数情况下都可以正常工作，但我意识到放大PDF文件时不会检测到手势（或调用手势）。因此，我无法通过滑动屏幕进入下一页。玩我创建的 extension PDFView {}函数时，我发现禁用subview中的用户交互功能使我能够检测到滑动手势。但是，现在我无法滚动PDFView中的页面。如果您能帮助我找出解决方法，我将不胜感激。

我想实现的是类似‎PDF Expert（https://apps.apple.com/us/app/pdf-expert-pdf-reader-editor/id743974925）的东西，在这里我可以水平滚动到下一页。

非常感谢您的提前帮助！

import UIKit
import PDFKit

//PDF Zoom scale
var scaleOfPdf: CGFloat = 4

extension PDFView {
    func disableBouncing(){
        for subview in subviews{
            if let scrollView = subview as? UIScrollView{
                scrollView.bounces = false
                return
            }
}

class ViewController: UIViewController,UIGestureRecognizerDelegate,UIDocumentPickerDelegate {

    @IBOutlet weak var pdfView: PDFView!
    
    override func viewDidLoad(){
        super.viewDidLoad()


            pdfView.autoresizesSubviews = true
            pdfView.autoresizingMask = [.flexibleWidth,.flexibleHeight,.flexibleTopMargin,.flexibleLeftMargin]
            
            pdfView.displayDirection = .horizontal
            pdfView.displayMode = .singlePage
            pdfView.autoScales = true
            // setting a color for background
            pdfView.backgroundColor = .black
            pdfView.document = pdfDocument
            //            pdfView.usePageViewController(true,withViewOptions: [UIPageViewController.OptionsKey.interPageSpacing: 20])
            pdfView.maxScaleFactor = 4.0
            pdfView.minScaleFactor = pdfView.scaleFactorForSizeToFit
            
            pdfView.disableBouncing()  


       //setting swipe gesture
        let leftSwipeGesture = UISwipeGestureRecognizer(target: self,action: #selector(respondLeftSwipeGesture(_:)))
        leftSwipeGesture.direction = [UISwipeGestureRecognizer.Direction.left]
        pdfView.addGestureRecognizer(leftSwipeGesture)
        
        let rightSwipeGesture = UISwipeGestureRecognizer(target: self,action: #selector(respondRightSwipeGesture(_:)))
        rightSwipeGesture.direction = [UISwipeGestureRecognizer.Direction.right]
        pdfView.addGestureRecognizer(rightSwipeGesture)

    }
    
        
    //setting swipe-gesture
    @objc func respondLeftSwipeGesture(_ sender: UISwipeGestureRecognizer) {
        print("left swipe was detected")
        if pdfView.document == nil { return }
        scaleOfPdf = pdfView.scaleFactor
        pdfView.goToNextPage(self)
        pdfView.scaleFactor = scaleOfPdf
    }
    
    @objc func respondRightSwipeGesture(_ sender: UISwipeGestureRecognizer) {
        print("right swipe was detected")
        if pdfView.document == nil { return }
        scaleOfPdf = pdfView.scaleFactor
        pdfView.goToPreviousPage(self)
        pdfView.scaleFactor = scaleOfPdf
    }
}

解决方法

手势识别器作为处理触摸的链条或流水线工作-一个（G1）失败后，第二个（G2）尝试识别其手势。在这里，您至少有4个识别器-您的2个识别器（left和right）和2个scrollView的识别器（pan和pinch）。我将提供仅涵盖scrollView的pan识别器的简短解决方案，如果您还会遇到pinch的问题-您将需要采用相同的方法。

假设G1是您的left识别器，而G2是scrollView的pan识别器。 为了使G2处理与G1相同的触摸，应告知它们同时识别。

此外，用户在垂直滚动时可能会稍微水平移动手指，因此在这种情况下，您还希望仅在G1放弃滑动但无法识别滑动之后才开始滚动。

为此，您应该将此代码添加到VC中。

override func viewDidLoad(){
    super.viewDidLoad()
    
    ...
    
    leftSwipeGesture.delegate = self
    leftSwipeGesture.cancelsTouchesInView = false
    rightSwipeGesture.delegate = self
    rightSwipeGesture.cancelsTouchesInView = false
}

optional func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer,shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    return gestureRecognizer == leftSwipeGesture
        || gestureRecognizer == rightSwipeGesture
        || otherGestureRecognizer == leftSwipeGesture
        || otherGestureRecognizer == rightSwipeGesture
}

optional func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer,shouldRequireFailureOf otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    guard let _ = gestureRecognizer as? UIPanGestureRecognizer else { return false }
    return otherGestureRecognizer == leftSwipeGesture
        || otherGestureRecognizer == rightSwipeGesture
}

optional func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer,shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    guard let _ = otherGestureRecognizer as? UIPanGestureRecognizer else { return false }
    return gestureRecognizer == leftSwipeGesture
        || gestureRecognizer == rightSwipeGesture
}

如果未调用我添加的UIGestureRecognizerDelegate方法，则需要创建一个子类PDFView，使left/rightSwipeGesture.delegate = pdfView并在PDFView子类中覆盖其{具有这种逻辑的{1}}方法。