iOS 11 PDFKit未更新注释位置

我正在开发一个在iPad上编辑PDF的应用程序。

我正在尝试使用我添加到PDFView的superview中的panGesture识别器来实现注释的拖动。问题是,注释的新矩形边界被分配,但更改不会反映在屏幕上。

这是我的代码:

@objc func handlePanGesture(panGesture: UIPanGestureRecognizer) {
    let touchLocation = panGesture.location(in: pdfView)

    guard let page = pdfView.page(for: touchLocation, nearest: true) else {
        return
    }
    let locationOnPage = pdfView.convert(touchLocation, to: page)

    switch panGesture.state {
    case .began:

           guard let annotation = page.annotation(at: locationOnPage) else {
                return
            }
            currentlySelectedAnnotation = annotation
    case .changed:

        guard let annotation = currentlySelectedAnnotation else {
            return
        }
        let initialBounds = annotation.bounds
        annotation.bounds = CGRect(origin: locationOnPage,
                                   size: initialBounds.size)

        print("move to \(locationOnPage)")
    case .ended, .cancelled, .failed:
        break
    default:
        break
    }
}

希望你能帮助我。