SwiftUI：自定义 UITextView UIViewRepresentable 需要在第一个操作上双击才能工作，此后单击可以正常工作

Question

我构建了这个小型演示视图，其中有两个 NoteRow，我的目标是能够按 return 键创建一个新行并使其成为急救人员。 这有效，但是，第一次创建新行，但它不会成为第一响应者。 return 键的后续点击既创建行又成为第一响应者。

知道这里出了什么问题吗？谢谢！

import SwiftUI
import Combine

struct FirstResponderDemo: View {
    
    @State private var rows: [NoteRow] = [
        .init(parentNoteId: "1", text: "foo"),
        .init(parentNoteId: "1", text: "bar"),
    ]
    
    @State private var activeRowId: String?
    
    var body: some View {
        ScrollViewReader { proxy in
            ScrollView {
                VStack {
                    ForEach(rows, id: \.id) { row in
                        ResponderTextView(
                            row: row,
                            text: $login,
                            activeRowId: $activeRowId,
                            returnPressed: returnPressed
                        )
                        .frame(width: 300, height: 44)
                    }
                }.padding(.horizontal, 12)
            }
        }
        .onAppear {
            self.activeRowId = rows[0].id
        }
    }
    
    private func returnPressed() {
        guard let id = activeRowId else { return }
        
        let newRow = NoteRow(parentNoteId: "1", text: "")
        print("new row id", newRow.id)
        
        if let index = rows.firstIndex(where: { [=10=].id == id }) {
            rows.insert(newRow, at: index + 1)
            activeRowId = newRow.id
        }
    }
}

struct FirstResponderDemo_Previews: PreviewProvider {
    static var previews: some View {
        FirstResponderDemo()
    }
}


struct ResponderView<View: UIView>: UIViewRepresentable {
    
    let row: NoteRow
    
    @Binding var activeRowId: String?
    
    var configuration = { (view: View) in }

    func makeUIView(context: Context) -> View { View() }

    func makeCoordinator() -> Coordinator {
        Coordinator(row: row, activeRowId: $activeRowId)
    }

    func updateUIView(_ uiView: View, context: Context) {
        context.coordinator.view = uiView
        
//        print(activeRowId)
        _ = activeRowId == row.id ? uiView.becomeFirstResponder() : uiView.resignFirstResponder()
        
        configuration(uiView)
    }
}

// MARK: - Coordinator

extension ResponderView {
    
    final class Coordinator {
    
        @Binding private var activeRowId: String?
        
        private var anyCancellable: AnyCancellable?
        
        fileprivate weak var view: UIView?

        init(row: NoteRow, activeRowId: Binding<String?>) {
            _activeRowId = activeRowId
            
            self.anyCancellable = Publishers.keyboardHeight.sink(receiveValue: { [weak self] keyboardHeight in
                guard let view = self?.view, let self = self else { return }
                
                DispatchQueue.main.async {
                    if view.isFirstResponder {
                        self.activeRowId = row.id
                        print("active row id is:", self.activeRowId)
                    }
                }
            })
        }
    }
    
}

// MARK: - keyboardHeight

extension Publishers {
    
    static var keyboardHeight: AnyPublisher<CGFloat, Never> {
        let willShow = NotificationCenter.default.publisher(for: UIApplication.keyboardWillShowNotification)
            .map { ([=10=].userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect)?.height ?? 0 }

        let willHide = NotificationCenter.default.publisher(for: UIApplication.keyboardWillHideNotification)
            .map { _ in CGFloat(0) }

        return MergeMany(willShow, willHide)
            .eraseToAnyPublisher()
    }
    
}

struct ResponderView_Previews: PreviewProvider {
    static var previews: some View {
        ResponderView<UITextView>.init(row: .init(parentNoteId: "1", text: "Hello world"), activeRowId: .constant(nil)) { _ in
        }.previewLayout(.fixed(width: 300, height: 40))
    }
}

struct ResponderTextView: View {
    
    let row: NoteRow
    
    @State var text: String
    
    @Binding var activeRowId: String?
    
    private var textViewDelegate: TextViewDelegate

    init(row: NoteRow, text: Binding<String>, activeRowId: Binding<String?>, returnPressed: @escaping () -> Void) {
        self.row = row
        self._text = State(initialValue: row.text)
        self._activeRowId = activeRowId
        self.textViewDelegate = TextViewDelegate(text: text, returnPressed: returnPressed)
    }

    var body: some View {
        ResponderView<UITextView>(row: row, activeRowId: $activeRowId) {
            [=10=].text = self.text
            [=10=].delegate = self.textViewDelegate
        }
    }
}

// MARK: - TextFieldDelegate

private extension ResponderTextView {
    
    final class TextViewDelegate: NSObject, UITextViewDelegate {
        
        @Binding private(set) var text: String
        
        let returnPressed: () -> Void

        init(text: Binding<String>, returnPressed: @escaping () -> Void) {
            _text = text
            self.returnPressed = returnPressed
        }
        
        func textViewDidChange(_ textView: UITextView) {
            DispatchQueue.main.async {
               self.text = textView.text
            }
        }
        
        func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
            if (text == "\n") {
                returnPressed()
                return false
            }
            
            return true
        }
    }

}

和NoteRow的定义：

final class NoteRow: ObservableObject, Identifiable {
    
    let id: String = UUID().uuidString
    
    let parentNoteId: String

    let text: String
   
    init(parentNoteId: String, text: String) {
        self.parentNoteId = parentNoteId
        self.text = text
    }
 
}

extension NoteRow: Equatable {
    
    static func == (lhs: NoteRow, rhs: NoteRow) -> Bool {
        lhs.id == rhs.id &&
        lhs.parentNoteId  == rhs.parentNoteId
    }
    
}

编辑： 调试更多

active row id is: Optional("71D8839A-D046-4DC5-8E02-F124779309E6") // 第一个默认行活动行 ID 是：可选（“5937B1D0-CBB0-4BE4-A235-4D57835D7B0F”）//第二个默认行

// 我按下了 return 键：新行 ID F640D1F9-0708-4099-BDA4-2682AF82E3BD 活动行 ID 为：可选（“5937B1D0-CBB0-4BE4-A235-4D57835D7B0F”）// 第二行的 ID 由于某种原因被设置为活动

// 之后，新行ID和活动行ID遵循预期路径：

新行 ID 9FDEB548-E19F-4572-BAD3-00E6CBB951D1 活动行 ID 为：可选（“9FDEB548-E19F-4572-BAD3-00E6CBB951D1”）

新行 ID 4B5C1AA3-15A1-4449-B1A2-9D834013496A 活动行 ID 为：可选（“4B5C1AA3-15A1-4449-B1A2-9D834013496A”）

新行 ID 22A61BE8-1BAD-4209-B46B-15666FF82D9B 活动行 ID 为：可选（“22A61BE8-1BAD-4209-B46B-15666FF82D9B”）

新行 ID 95DD6B33-4421-4A32-8478-DCCBCBB1824E 活动行 ID 为：可选（“95DD6B33-4421-4A32-8478-DCCBCBB1824E”）

Answer 1

好吧，我不知道这段代码，但下面修复了有问题的情况（用 Xcode 12b 测试）

    if (text == "\n") {
        DispatchQueue.main.async {     // << defer to next event !!
            self.returnPressed()
        }
        return false
    }
    return true
}

SwiftUI：自定义 UITextView UIViewRepresentable 需要在第一个操作上双击才能工作，此后单击可以正常工作

SwiftUI: Custom UITextView UIViewRepresentable requires double tap on the first action to work, works fine with single taps thereafter

swift

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