PDFView - 适合 2 页的高度和宽度启用滚动到下一页

Question

我有一个视图，其中包含来自 PDFKit 的 PDFView。我想在屏幕上同时看到 2 个完整页面，并且它们需要适合高度和宽度。我可以看到两种方法，但都不是完美的：

选项 1）使用 .twoUpContinously 显示模式 - 这里它适合宽度，但高度在 PDF 的约 2/3 中被裁剪。

lazy var pdfView: PDFView = {
    let view = PDFView().layoutable()
    view.displayMode = .twoUpContinuous // !
    view.displayDirection = .vertical
    view.minScaleFactor = view.scaleFactorForSizeToFit
    view.maxScaleFactor = 3
    view.autoScales = true
    return view
}()

选项 2）使用 .twoUp 显示模式 - 这里它适合宽度和高度，但手势识别器不会记录向下滑动，因此用户无法将页面更改为 3 和 4。

lazy var pdfView: PDFView = {
    let view = PDFView().layoutable()
    view.displayMode = .twoUp // !
    view.displayDirection = .vertical
    view.minScaleFactor = view.scaleFactorForSizeToFit
    view.maxScaleFactor = 3
    view.autoScales = true
    return view
}()

是否有内置的- 这种情况的解决方案..？或者我是否必须添加手动滑动手势识别器并基于 .twoUp 解决方案更改页面..？

Answer 1

所以最后我想到了3个解决方案，但都不是完美的。我最喜欢解决方案3。

---

解决方案 1：不稳定，有时无法渲染 pdf 或启动时不在第一页。但大多数情况下工作正常。

lazy var pdfView: PDFView = {
    let view = PDFView().layoutable()
    view.displayMode = .twoUpContinuous
    view.autoScales = false
    view.displayDirection = .vertical
    return view
}()

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    updatePDFViewScaling()
}
override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    updatePDFViewScaling()
}
override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    updatePDFViewScaling()
}
private func updatePDFViewScaling() {
    customView.pdfView.displayMode = .twoUp
    let scaleFactor = customView.pdfView.scaleFactorForSizeToFit
    customView.pdfView.displayMode = .twoUpContinuous
    customView.pdfView.scaleFactor = scaleFactor
    customView.pdfView.minScaleFactor = scaleFactor
    customView.pdfView.maxScaleFactor = 3
}

---

解决方案2：水平方向完美，垂直方向则不然。适合 2 个 PDF 的宽度，但底部被裁剪。对于 A4 文档，在大多数 iPad 上不应裁剪太多，因为它们的宽高比均为 3:4。

lazy var pdfView: PDFView = {
    let view = PDFView().layoutable()
    view.displayMode = .twoUpContinuous
    view.displayDirection = .vertical
    view.minScaleFactor = view.scaleFactorForSizeToFit
    view.maxScaleFactor = 3
    return view
}()

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    customView.pdfView.autoScales = true
}
override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    customView.pdfView.autoScales = true
}
override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    customView.pdfView.autoScales = true
}

---

解决方案 3：当您用手指滚动到 PDF 内的下一页/上一页时，没有动画。

lazy var pdfView: PDFView = {
    let view = PDFView().layoutable()
    view.displayMode = .twoUp
    view.displayDirection = .vertical
    view.minScaleFactor = view.scaleFactorForSizeToFit
    view.maxScaleFactor = 3
    view.autoScales = true
    return view
}()
// somewhere in view's init or wherever you want
    let upGestureRegocnizer = UISwipeGestureRecognizer(target: self, action: #selector(upSwipeAction(gestureRegonizer:)))
    upGestureRegocnizer.direction = .up
    pdfView.addGestureRecognizer(upGestureRegocnizer)
    let downGestureRegocnizer = UISwipeGestureRecognizer(target: self, action: #selector(downSwipeAction(gestureRegonizer:)))
    downGestureRegocnizer.direction = .down
    pdfView.addGestureRecognizer(downGestureRegocnizer)

@objc private func upSwipeAction(gestureRegonizer: UISwipeGestureRecognizer) {
    guard pdfView.canGoToNextPage else { return }
    pdfView.goToNextPage(self)
}
@objc private func downSwipeAction(gestureRegonizer: UISwipeGestureRecognizer) {
    guard pdfView.canGoToPreviousPage else { return }
    pdfView.goToPreviousPage(self)
}