为UiviewRementable ScrollView（SwiftUi）设置ContentOffset

Question

问题

我正在尝试使用给定的缩放和位置启动UiviewSrentable scrollview的

。我在MakeUiview中设置了新的Zoom和新的ContentOffset，但是SetContentOffset调用没有视觉效果，并且在从新的Zoom中重新放大时，ScrollView会移动内容，就好像SetContentOffSet一样效果。

我在做什么错？

下面的代码

是uiviewermesentable的整个代码。我标记了最相关的行，并带有“请参阅此处”评论。

import SwiftUI

struct ZoomableScrollView<Content: View>: UIViewRepresentable {
    @EnvironmentObject var drawingModel: DrawingModel
    private var content: Content
    let screenScale: CGFloat
    
    init(screenScale: CGFloat, @ViewBuilder content: () -> Content) {
        self.screenScale = screenScale
        self.content = content()
    }

    func makeUIView(context: Context) -> UIScrollView {
        // set up the UIScrollView
        let scrollView = UIScrollView()
        scrollView.delegate = context.coordinator  // for viewForZooming(in:)

        let fullPageZoomScale = 0.85 * screenScale // screenScale is a constant
        scrollView.maximumZoomScale = fullPageZoomScale * 10
        scrollView.minimumZoomScale = fullPageZoomScale
        scrollView.zoomScale = fullPageZoomScale
        scrollView.bouncesZoom = true
        scrollView.delaysContentTouches = false

        // create a UIHostingController to hold our SwiftUI content
        let hostedView = context.coordinator.hostingController.view!
        hostedView.translatesAutoresizingMaskIntoConstraints = true
        hostedView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        hostedView.frame = scrollView.bounds
        scrollView.addSubview(hostedView)
        
        /// -------- SEE HERE These two lines does not work as intended
        scrollView.setZoomScale(0.5319657829374683, animated: false)
        scrollView.setContentOffset(CGPoint(x: 518.5, y: 330.0), animated: false)
        /// -----
        
        return scrollView
    }

    func makeCoordinator() -> Coordinator {
        return Coordinator(hostingController: UIHostingController(rootView: self.content),
                           userScrolledAction: drawingModel.userScrollAction,
                           userZoomedAction: drawingModel.userZoomAction)
    }

    func updateUIView(_ uiView: UIScrollView, context: Context) {
        // update the hosting controller's SwiftUI content
        context.coordinator.hostingController.rootView = self.content
        assert(context.coordinator.hostingController.view.superview == uiView)
    }

    /// MARK: - Coordinator
    class Coordinator: NSObject, UIScrollViewDelegate {
        var hostingController: UIHostingController<Content>
        let userScrolledAction: (CGPoint) -> Void
        let userZoomedAction: (CGFloat) -> Void

        init(hostingController: UIHostingController<Content>, userScrolledAction: @escaping (CGPoint) -> Void, userZoomedAction: @escaping (CGFloat) -> Void) {
            self.hostingController = hostingController
            self.userScrolledAction = userScrolledAction
            self.userZoomedAction = userZoomedAction
        }

        func viewForZooming(in scrollView: UIScrollView) -> UIView? {
            return hostingController.view
        }

        func scrollViewDidScroll(_ scrollView: UIScrollView) {
            userScrolledAction(scrollView.contentOffset)
        }

        func scrollViewDidZoom(_ scrollView: UIScrollView) {
            userZoomedAction(scrollView.zoomScale)
        }
    }
}

Answer 1

应该进入

func updateUIView(_ uiView: UIScrollView, context: Context)