UIViewRepresentable不更新swiftui中的發布/系結屬性 -有解無憂

我試圖在SwiftUI中包裝UIScrollView以獲得一些額外的功能。我想訪問UIScrollView的contentOffset屬性，并將其分配給SwiftUI的一些屬性（Published 或系結），但SwiftUI（我的ContentView）沒有檢測到任何屬性變化。你能幫我解決這個問題嗎？

這是我的UIScrollView

import SwiftUI
import UIKit

struct MyScrollView<Content: View>。UIViewRepresentable {
    
    @ObservedObject var viewModel: ViewModel var viewModel.
    @ViewBuilder var content: () -> Content
   
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    class Coordinator: NSObject, UIScrollViewDelegate {
        var parent: MyScrollView

        init(_ parent: MyScrollView) {
            self.parent = parent
        }
        
        func scrollViewDidScroll(_ scrollView: UIScrollView) {
           parent.viewModel.scrollviewContentOffset = scrollView.contentOffset.y
        }
        
    }
    
    func makeUIView（context: Context) -> UIScrollView {
        let scrollView = UIScrollView()
        
        scrollView.delegate = context.coordinator
        scrollView.isScrollEnabled = true
        
        let child = UIHostingController（rootView: content()
        scrollView.addSubview(child.view)
        
        let newSize = child.view.sizeThatFits(CGSize（width: UIScreen.screenWidth, height: UIScreen.screenHeight))
        child.view.frame = CGRect（x: 0, y: 0, width: newSize.width, height: newSize.height)
        
        scrollView.contentSize = newSize
        
        return scrollView
    }
    
    func updateUIView(_ uiView: UIScrollView, context: Context) {
        //
    }
    
    typealias UIViewType = UIScrollView
}

而這是我的ContentView

import SwiftUI

class ViewModel。ObservableObject {
    @Published var scrollviewContentOffset = CGFloat.零
}

struct ContentView: View {
    
    @StateObject private var viewModel = ViewModel()
    
    var body。some View {
        MyScrollView(viewModel: viewModel) {
            ForEach(0...< 100) { i in
                Text("（i）")
                    .offset(y: viewModel.scrollviewContentOffset / CGFloat(i   1)
            }
        }
    }
}

CodePudding

在創建你的MyScrollView時，你只捕獲了初始的內容，而沒有在視圖模型改變時更新它。

您需要在updateUIView內設定更新的content。例如，你可以將hostingController存盤在Coordinator里面：

struct MyScrollView<Content: View>。UIViewRepresentable {

    @StateObject var viewModel: ViewModel
    @ViewBuilder var content: () -> Content

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    class Coordinator: NSObject, UIScrollViewDelegate {
        let parent: MyScrollView
        var hostingController: UIHostingController<Content> !

        init(_ parent: MyScrollView) {
            self.parent = parent
        }

        func scrollViewDidScroll(_ scrollView: UIScrollView) {
            parent.viewModel.scrollviewContentOffset = scrollView.contentOffset.y
        }

    }

    func makeUIView（context: Context) -> UIScrollView {
        let scrollView = UIScrollView()

        scrollView.delegate = context.coordinator
        scrollView.isScrollEnabled = true

        let child = UIHostingController（rootView: content()
        context.coordinator.hostingController = child
        scrollView.addSubview(child.view)

        let newSize = child.view.sizeThatFits(CGSize(width: UIScreen.main.bound.width, height: UIScreen.main.bounds.height))
        child.view.frame = CGRect（x: 0, y: 0, width: newSize.width, height: newSize.height)

        scrollView.contentSize = newSize

        return scrollView
    }

    func updateUIView(_ uiView: UIScrollView, context: Context) {
        context.coordinator.hostingController.rootView = content（)
    }
}

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