带有 UIViewcontrollerRepresentable 的自定义 UIViewController 具有在 SwiftUI 中调用时崩溃或为零的 UITextView

Question

我做了一个自定义的 UIViewController 叫 ViewControllerA 并且希望能够使用它所以我做了一个叫 ViewControllerARepresentable 的 UIViewControllerRepresentable 如下所示，问题虽然是当我在我的 SwiftUI 视图中调用 ViewControllerARepresentable 并为 stringToUpdateTextView 传递一个值时，ViewControllerA 表示 ViewControllerA 中的 htmlTextView(UITextView) 是 nil 我不确定为什么。

ViewControllerARepresentable(stringToUpdateTextView: "<html>Send some Html Text as string here</html>")

ViewControllerARepresentable

public struct ViewControllerARepresentable: UIViewControllerRepresentable {
  var stringToUpdateTextView: String

  public func makeUIViewController(context: Context) -> ViewControllerA {
    let viewcontrollerA = ViewControllerA(testString: testingString)

    return viewcontrollerA
  }

  public func updateUIViewController(_ uiViewController: ViewControllerA, context: Context) {}
}

ViewControllerA

open class ViewControllerA: UIViewController {

  public var stringToUpdateTextView: String

  override open func viewDidLoad() {
    super.viewDidLoad()

htmlTextView.text = stringToUpdateTextView
  }

  @IBOutlet weak var htmlTextView: UITextView!

  public init(testString: String) {
    self.testString = testString
    super.init(nibName: nil, bundle: nil)
  }

  required public init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
}

崩溃发生在 htmlTextView.text = stringToUpdateTextView，表明 htmlTextView.text 为零，即使它是一个 IBOutlet。如果在 viewDidAppear 或 viewDidLoad

中调用，对 htmlTextView 所做的任何更改（如背景颜色等）也会导致崩溃

Answer 1

在 makeUIViewController 中实例化视图控制器时，插座尚未初始化。

以下代码从情节提要中加载您的视图控制器，并更新 updateUIViewController 中的属性：

ViewController.swift

import UIKit
import SwiftUI

class ViewController: UIViewController {

  @IBOutlet weak var htmlTextView: UITextView!

  override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
  }

}

struct ViewControllerWrapper: UIViewControllerRepresentable {
  typealias UIViewControllerType = ViewController

  @Binding var text: String

  func makeUIViewController(context: Context) -> ViewController {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    guard let viewController =  storyboard.instantiateViewController(
      identifier: "ViewController") as? ViewController else {
        fatalError("Cannot load from storyboard")
    }
    return viewController
  }

  func updateUIViewController(_ uiViewController: ViewController, context: Context) {
    uiViewController.htmlTextView.text = text
  }

}


struct ViewControllerPreview: PreviewProvider {
  static var previews: some View {
    ViewControllerWrapper(text: .constant("hello world!"))
  }
}

SwiftUIView.swift

struct SwiftUIView: View {
  @State var text = "Text"
  var body: some View {
    HStack {
      TextField("Text:", text: $text)
      ViewControllerWrapper(text: $text)
    }
  }
}

带有 UIViewcontrollerRepresentable 的自定义 UIViewController 具有在 SwiftUI 中调用时崩溃或为零的 UITextView

Custom UIViewController with UIViewcontrollerRepresentable that has a UITextView that crashes or is nil when called in SwiftUI

nsattributedstring

swiftui

uiviewcontrollerrepresentable