swiftui - UIViewControllerRepresentable 中包含的@Binding 未更新

Question

我有一个 UIHostingController包含在 UIViewControllerRepresentable包含对绑定(bind)的引用。当绑定(bind)改变时，updateUIViewController被调用，但底层 View 不会自动重新渲染。如何向嵌入式 UIHostingController 发送信号它需要更新其内容吗？

以下是该场景的简化版本。请注意，当步进器发生变化时，第一个 Text自动更新，但 PassthroughView 中包含的文本UIViewControllerRepresentable不会自动看到其内容被重新渲染。

import SwiftUI

struct ContentView: View {
    @State var number = 99

    var body: some View {
        VStack {
            Stepper("Stepper", value: $number)
            Text("Direct Value: \(number)")
            PassthroughView {
                Text("Passthrough Value: \(number)")
            }
            Spacer()
        }.font(.headline)
    }
}

struct PassthroughView<V: View> : UIViewControllerRepresentable {
    typealias UIViewControllerType = UIHostingController<V>
    let content: V

    init(@ViewBuilder _ content: () -> V) {
        self.content = content()
    }

    func makeUIViewController(context: UIViewControllerRepresentableContext<PassthroughView<V>>) -> UIViewControllerType {
        UIViewControllerType(rootView: content)
    }

    func updateUIViewController(_ controller: UIViewControllerType, context: UIViewControllerRepresentableContext<PassthroughView<V>>) {
        // this is called when the binding changes;
        // how to tell the UIHostingController to re-render?
    }
}

Answer 1

以下代码将按需要工作:

我不确定这是否是一种好习惯，因为我对 UIKit 不是很熟悉。

struct PassthroughView<V: View> : UIViewControllerRepresentable {
    typealias UIViewControllerType = UIHostingController<V>
    let content: V

    init(@ViewBuilder _ content: () -> V) {
        self.content = content()
    }

    func makeUIViewController(context: UIViewControllerRepresentableContext<PassthroughView<V>>) -> UIViewControllerType {
        UIViewControllerType(rootView: content)
    }

    func updateUIViewController(_ controller: UIViewControllerType, context: UIViewControllerRepresentableContext<PassthroughView<V>>) {
        // this is called when the binding changes;
        // how to tell the UIHostingController to re-render?
        controller.rootView = content
    }
}

struct ContentView: View {

    @State var number = 99

    var body: some View {
        VStack {
            Stepper("Stepper", value: $number)
            Text("Direct Value: \(number)")
            PassthroughView {
                Text("Passthrough Value: \(number)")
            }
            Spacer()
        }.font(.headline)
    }

}

我希望这有帮助!