import UIKit final class RDPDFReaderPageChildViewController: UIViewController { let contentView: UIView let page: Int init(contentView: UIView, page: Int) { self.contentView = contentView self.page = page super.init(nibName: nil, bundle: nil) } required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") } override func loadView() { // 页面控制器只拥有稳定的外壳;实际 PDF 内容页可在放大时临时迁移到 // Zoom Overlay,退出时再回到此处,而不会破坏 UIPageViewController 的层级。 let container = UIView() container.backgroundColor = .clear container.addSubview(contentView) contentView.frame = container.bounds contentView.autoresizingMask = [.flexibleWidth, .flexibleHeight] view = container } }