Swift iOS15 PDFKit下PDFView缩放后屏幕边缘手势无法识别问题

问题原因 #

1. 你实现的shouldRecognizeSimultaneouslyWith代理方法未生效，是因为没有给两个UIScreenEdgePanGestureRecognizer的delegate属性赋值为当前控制器，系统不会主动调用你写的代理逻辑。
2. 边缘手势加在pdfView上，当PDF缩放时，pdfView内部的滚动视图会优先消费边缘滑动事件，导致手势无法触发。

修复步骤 #

1. 首先让当前控制器遵守UIGestureRecognizerDelegate协议：

class TextDocumentViewController: UIViewController, UIGestureRecognizerDelegate {
    // 你的原有代码
}

2. 修改viewDidLoad中的手势添加逻辑，将手势加在控制器根视图上，同时设置代理：

override func viewDidLoad(){
    super.viewDidLoad()

    // 左边缘翻页手势
    let leftScreenEdgeRecognizer = UIScreenEdgePanGestureRecognizer (
        target: self, action: #selector(leftEdgePanGestureHandler(_ : )))
    leftScreenEdgeRecognizer.edges = .left
    leftScreenEdgeRecognizer.delegate = self
    
    // 右边缘翻页手势
    let rightScreenEdgeRecognizer = UIScreenEdgePanGestureRecognizer (
        target: self, action: #selector(rightEdgePanGestureHandler(_ : )))
    rightScreenEdgeRecognizer.edges = .right
    rightScreenEdgeRecognizer.delegate = self
    
    // 手势添加到控制器根视图，而非pdfView
    view.addGestureRecognizer(leftScreenEdgeRecognizer)
    view.addGestureRecognizer(rightScreenEdgeRecognizer)
}

3. 保留原有多手势识别代理方法，可额外添加优先级逻辑确保边缘手势优先触发：

// 允许边缘手势和其他手势同时识别
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    return gestureRecognizer is UIScreenEdgePanGestureRecognizer
}

// 可选：设置边缘手势优先级更高，进一步确保触发
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    return gestureRecognizer is UIScreenEdgePanGestureRecognizer
}

你原来的手势触发逻辑无需修改。

内容的提问来源于stack exchange，提问作者user8460166