检测到PDFView确实滚动

Question

iOS上的PDFKit是否公开了PDFView的底层UIScrollView，或者是否有其他方法可以直接检测用户是否滚动了PDFView？

我的用例是在文档滚动时隐藏一个导航栏，因此作为一种变通方法，我在PDFView的父级中添加了自己的平移手势识别器，并在gestureRecognizerShouldBegin中进行了隐藏，总是返回false，但我希望文档中缺少更多像UIScrollViewDelegate这样的东西。

Answer 1

尝尝这个,

NotificationCenter.default.addObserver(self, selector: #selector(handlePageChange(notification:)), name: Notification.Name.PDFViewPageChanged, object: nil)

@objc private func handlePageChange(notification: Notification)
{
    print("Page changed")
}

Answer 2

我这样做是为了检测pdfView上的缩放和平移，以便将这些手势复制到另一个pdfView上，它在这里工作得很好。通过我在这里找到的PanDirectionGestureRecognizer获得了一些检测垂直和水平平移的帮助：stackoverflow.com/a/55635482/558112

class Document: UIViewController, UIScrollViewDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        // Subscribe to notifications.
        NotificationCenter.default.addObserver(self, selector: #selector(onPageZoomAndPan), name: .PDFViewScaleChanged, object: pdfView

        // get the scrollView in pdfView and attach gesture recognizers

        outerLoop: for subView in pdfView.subviews {
            for view in subView.subviews {
                if let scrollView = view as? UIScrollView {
                    let xScrollViewPanGesture = PanDirectionGestureRecognizer(direction: .horizontal, target: self, action: #selector(onPageZoomAndPan))
                    xScrollViewPanGesture.delegate = self
                    scrollView.addGestureRecognizer(xScrollViewPanGesture)

                    let yScrollViewPanGesture = PanDirectionGestureRecognizer(direction: .vertical, target: self, action: #selector(onPageZoomAndPan))
                    yScrollViewPanGesture.delegate = self
                    scrollView.addGestureRecognizer(yScrollViewPanGesture)

                    break outerLoop
                }
            }
        }
    }

    // MARK: - UIScrollViewDelegate

    @objc private func onPageZoomAndPan() {
        let rect = pdfView.convert(pdfView.bounds, to: pdfView.currentPage!)
        pdfViewSecondScreen.scaleFactor = pdfView.scaleFactor
        pdfViewSecondScreen.go(to: rect, on: pdfView.currentPage!)
    }
}



enum PanDirection {
    case vertical
    case horizontal
}


// UIKit.UIGestureRecognizerSubclass

import UIKit.UIGestureRecognizerSubclass

class PanDirectionGestureRecognizer: UIPanGestureRecognizer {

    let direction : PanDirection

    init(direction: PanDirection, target: AnyObject, action: Selector) {
        self.direction = direction
        super.init(target: target, action: action)
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesMoved(touches, with: event)

        if state == .began {
            let vel = velocity(in: self.view!)

            switch direction {
            case .horizontal where abs(vel.y) > abs(vel.x):
                state = .cancelled
            case .vertical where abs(vel.x) > abs(vel.y):
                state = .cancelled
            default:
                break
            }
        }
    }
} 

Answer 3

在iOS上的PDFKit确实公开了PDFView的底层UIScrollView

不，但希望苹果在未来会增加这一点。我记得UIWebView最初没有它，后来又添加了它。

，或者是否有任何其他方法可以直接检测到用户滚动了PDFView

不，看起来PDFViewDelegate提供的通知都没有解决这个问题。

我正在从UIWebView迁移到PDFView，并且使用scrollViewDidScroll来做很多事情，所以我不想仅仅依赖于添加一个手势识别器。根据@Matthijs的回答，我在PDFView中找到了UIScrollView，让我的类成为它的委托，然后将任何事件传递回滚动视图(在我的类成为委托之前，滚动视图是它自己的委托)，这样它也可以响应它们。在UIWebView中，这最后一步是不必要的，但在PDFView中，没有它，缩放和其他可能的功能将无法工作。

我正在覆盖所有有文档记录的委托方法，以减少如果苹果更改PDFView的内部函数，它将崩溃的可能性。但是，我必须检查每个方法中的respondsToSelector，因为最初的滚动视图委托目前并没有实现所有这些方法。

- (void)viewDidLoad {
    // create the PDFView and find its inner scrollView
    self.pdfView = [[PDFView alloc] init];
    for (UIView *subview in self.pdfView.subviews) {
        if ([subview isKindOfClass:[UIScrollView class]]) {
            self.scrollView = (UIScrollView *)subview;
        } else {
            for (UIView *subsubview in subview.subviews) {
                if ([subsubview isKindOfClass:[UIScrollView class]]) {
                    self.scrollView = (UIScrollView *)subsubview;
                }
            }
        }
    }
}

- (void)loadPDFDocument:(NSString *)URL {
    // load a document, then become the delegate for the scrollView (we have to do that after loading the document)
    PDFDocument *document = [[PDFDocument alloc] initWithURL:URL];
    self.pdfView.document = document;
    self.scrollView.delegate = self;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    // *** respond to scroll events here ***

    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewDidScroll:)]) {
        [scrollViewDelegate scrollViewDidScroll:scrollView];
    }
}

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewWillBeginDragging:)]) {
        [scrollViewDelegate scrollViewWillBeginDragging:scrollView];
    }
}

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)]) {
        [scrollViewDelegate scrollViewWillEndDragging:scrollView withVelocity:velocity targetContentOffset:targetContentOffset];
    }
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewDidEndDragging:willDecelerate:)]) {
        [scrollViewDelegate scrollViewDidEndDragging:scrollView willDecelerate:decelerate];
    }
}

- (BOOL)scrollViewShouldScrollToTop:(UIScrollView *)scrollView {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewShouldScrollToTop:)]) {
        return [scrollViewDelegate scrollViewShouldScrollToTop:scrollView];
    }
    return TRUE;
}

- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewDidScrollToTop:)]) {
        [scrollViewDelegate scrollViewDidScrollToTop:scrollView];
    }
}

- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewWillBeginDecelerating:)]) {
        [scrollViewDelegate scrollViewWillBeginDecelerating:scrollView];
    }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewDidEndDecelerating:)]) {
        [scrollViewDelegate scrollViewDidEndDecelerating:scrollView];
    }
}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(viewForZoomingInScrollView:)]) {
        return [scrollViewDelegate viewForZoomingInScrollView:scrollView];
    }
    return nil;
}

- (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(UIView *)view {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewWillBeginZooming:withView:)]) {
        [scrollViewDelegate scrollViewWillBeginZooming:scrollView withView:view];
    }
}

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewDidEndZooming:withView:atScale:)]) {
        [scrollViewDelegate scrollViewDidEndZooming:scrollView withView:view atScale:scale];
    }
}

- (void)scrollViewDidZoom:(UIScrollView *)scrollView {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewDidZoom:)]) {
        [scrollViewDelegate scrollViewDidZoom:scrollView];
    }
}

- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewDidEndScrollingAnimation:)]) {
        [scrollViewDelegate scrollViewDidEndScrollingAnimation:scrollView];
    }
}

- (void)scrollViewDidChangeAdjustedContentInset:(UIScrollView *)scrollView {
    UIScrollView <UIScrollViewDelegate> *scrollViewDelegate = (UIScrollView <UIScrollViewDelegate> *)self.scrollView;
    if ([scrollViewDelegate respondsToSelector:@selector(scrollViewDidChangeAdjustedContentInset:)]) {
        [scrollViewDelegate scrollViewDidChangeAdjustedContentInset:scrollView];
    }
}