使用自定义 UITextField（通过使用 UIViewRepresentable）作为子视图时列表视图的奇怪行为

Question

我注意到，当我们在 UIViewRepresentable 协议的帮助下使用 UITextfield 作为 SwiftUI 列表的子视图时，绑定无法按预期工作。

我已经使用列表视图和自定义文本字段视图实现了类似动态表单的功能，当我尝试更新列表中除第一个字段之外的一个字段的值时，当点击附件视图的完成按钮时，先前更新的元素数据将被删除文本字段视图。

相关的代码片段

我添加了下面与自定义文本字段、列表行和 ListView 主体TextField View

struct TextFieldView: UIViewRepresentable {
  
 // MARK: - Internal Properties
  
 private let inputTextField = UITextField()
 public var placeholder: String
 public var keyboardType: UIKeyboardType
 private let actionsHandler = InputAccessoryViewActionsHandler()
  
 @Binding public var value: String?
  
 func makeUIView(context: Context) -> UITextField {
   
  inputTextField.placeholder = placeholder
  inputTextField.textColor = AppTheme.primaryText.color
  inputTextField.font = Font.Roboto.regular.of(size: 16)
  inputTextField.keyboardType = keyboardType
  inputTextField.delegate = context.coordinator
  inputTextField.accessibilityIdentifier = "specValueTextField"
  inputTextField.isAccessibilityElement = true
   
  if keyboardType == .numberPad {
   configureAccessoryView()
  }
  return inputTextField
 }
  
 func updateUIView(_ uiView: UITextField, context: Context) {
  if let value = self.value {
   uiView.text = value
  }
 }
  
 func makeCoordinator() -> Coordinator {
  Coordinator($value)
 }
  
 func configureAccessoryView() {
  // Accessory View
  let toolbar = UIToolbar()
  toolbar.sizeToFit()
  let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace,
                    target: nil,
                    action: nil)
  let doneButton = UIBarButtonItem(title: "Done".localized,
                   style: .plain,
                   target: self.actionsHandler,
                   action: #selector(self.actionsHandler.doneButtonAction))
  doneButton.tintColor = AppTheme.primary.color
  doneButton.accessibilityIdentifier = "Done"
   
  toolbar.setItems([flexibleSpace, doneButton], animated: true)
   
  self.actionsHandler.doneButtonTapped = {
   self.value = self.inputTextField.text
   self.inputTextField.resignFirstResponder()
  }
  self.inputTextField.inputAccessoryView = toolbar
 }
  
 class InputAccessoryViewActionsHandler {
  public var doneButtonTapped: (() -> Void)?
   
  @objc func doneButtonAction() {
   self.doneButtonTapped?()
  }
 }
  
 class Coordinator: NSObject, UITextFieldDelegate {
  var text: Binding<String?>
   
  init(_ text: Binding<String?>) {
   self.text = text
  }
   
  func textField(_ textField: UITextField,
          shouldChangeCharactersIn range: NSRange,
          replacementString string: String) -> Bool {
   if let currentValue = textField.text as NSString? {
    let proposedValue = currentValue.replacingCharacters(in: range, with: string)
    self.text.wrappedValue = proposedValue
   }
   return true
  }
  func textFieldShouldReturn(_ textField: UITextField) -> Bool {
   textField.resignFirstResponder()
   return true
  }
 }
}

List Row Element view

struct SpecificationRow: View {
  @Binding var specification: ClassificationSpecItem
 // MARK: - Body
  
 var body: some View {
  VStack(alignment: .leading) {
   TextFieldView(placeholder: "Enter value",
          keyboardType: keyboardType,
          value: $specification.specValue)
  }.padding(EdgeInsets(top: 12, leading: 0, bottom: 5, trailing: 0))
 }
}

，列表主体如下所示

  var body: some View {
  VStack {
   List($viewModel.specifications) { $spec in
       SpecificationRow(specification: $spec)
}
}

viewModel 已确认为 ObservableObject，并且规范属性是 @Published 属性

我遗漏了什么吗？或者这只是 SwiftUI 中的一个错误？任何帮助将不胜感激！谢谢！

Answer 1

您在错误的位置创建视图对象。而不是：

private let inputTextField = UITextField()

do:

private let inputTextField: UITextField?

func makeUIView(context: Context) -> UITextField {
    inputTextField = UITextField()

或者也许您不需要保留参考文献？

此外，您无法在 SwiftUI 中创建这样的对象：

private let actionsHandler = InputAccessoryViewActionsHandler()

您可以使用协调器对象来进行操作处理。

SwiftUI View 结构应该只初始化值类型。如果实例化对象，则需要将其包装在 @StateObject 中，它将生命周期与 View 的出现/消失相关联，或者如果与应用程序的生命周期相关联，则可以是全局或单例。

另外，在 updateUIView 中，您需要从属性中更新文本字段属性。

Answer 2

您正在 updateUIView 方法而不是 TextFieldView 类的 makeUIView 中更新文本字段值。

只需将您的代码替换为以下代码即可

func makeUIView(context: Context) -> UITextField {

 //Assign your value to UITextField here
 inputTextField.text = self.value

 inputTextField.placeholder = placeholder
 inputTextField.textColor = AppTheme.primaryText.color
 inputTextField.font = Font.Roboto.regular.of(size: 16)
 inputTextField.keyboardType = keyboardType
 inputTextField.delegate = context.coordinator
 inputTextField.accessibilityIdentifier = "specValueTextField"
 inputTextField.isAccessibilityElement = true

 if keyboardType == .numberPad {
   configureAccessoryView()
 }
 return inputTextField

} 

func updateUIView(_ uiView: UITextField, context: Context) {

   //Comment below code
 
   /* if let value = self.value {
      uiView.text = value
   }*/

}