用于 UITextView 的 SwiftUI 包装器不更新 ObservedObject

Question

我希望我错了，但我一直无法找到与可编辑 UITextView 等效的 SwiftUI。因此，我使用 UIViewRepresentable 构建了一个。使用 ObservableObject 填充 SwiftUI 文本和我自己的视图有效 - 但在我的视图中所做的更新不会传播到 ObservableObject。我一定在绑定概念中遗漏了一些重要的东西。任何指导将不胜感激。

import SwiftUI
import Combine

struct ContentView: View {

    @ObservedObject var myOText: MyOText

    var body: some View {
        ScrollView {
            VStack {
                Text("This is a bound Text View")
                    .padding(.top, 10)
                    .font(.headline)

                Text(myOText.inTheCourse)
                    .lineLimit(3)
                    .padding()

                Text("This is a multi-line UITextView wrapper:")
                    .font(.headline)

                MultilineTextView(myOText: myOText)
                    .frame(height: 100)
                    .padding()

                Spacer()
            }
        }
    }
}

struct MultilineTextView: UIViewRepresentable {

    @ObservedObject var myOText: MyOText

    func makeUIView(context: Context) -> UITextView {
        let view = UITextView()
        view.isScrollEnabled = true
        view.isEditable = true
        view.isUserInteractionEnabled = true
        view.textAlignment = .center
        view.font = UIFont(name: "Times New Roman", size: 20)
        return view
    }

    func updateUIView(_ uiView: UITextView, context: Context) {
        uiView.text = myOText.inTheCourse
    }
}

class MyOText: ObservableObject {
    @Published var inTheCourse: String = "When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them ..."
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView(myOText: MyOText())
    }
}

Xcode 版本 11.2 beta 2 (11B44)，iOS 13。

Answer 1

你的多行文本视图需要一个协调器来观察 UITextView 的文本更新

struct MultilineTextView: UIViewRepresentable {
    @ObservedObject var myOText: MyOText

    func makeUIView(context: Context) -> UITextView {
        let view = UITextView()
        view.isScrollEnabled = true
        view.isEditable = true
        view.isUserInteractionEnabled = true
        view.textAlignment = .center
        view.font = UIFont(name: "Times New Roman", size: 20)
        view.delegate = context.coordinator
        return view
    }

    func updateUIView(_ uiView: UITextView, context: Context) {
        uiView.text = myOText.inTheCourse
    }

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

    class Coordinator: NSObject, UITextViewDelegate {
        var control: MultilineTextView

        init(_ control: MultilineTextView) {
            self.control = control
        }

        func textViewDidChange(_ textView: UITextView) {
            control.myOText.inTheCourse = textView.text
        }
    }
}