SwiftUI 中自定义 UIViewRepresentable UITextView 的框架高度问题

Question

我正在通过 UIViewRepresentable 为 SwiftUI 构建自定义 UITextView。 它旨在显示NSAttributedString ，并处理链接按下。 一切正常，但是当我在带有内联标题的NavigationView显示此视图时，框架高度完全混乱。

import SwiftUI

struct AttributedText: UIViewRepresentable {
  class Coordinator: NSObject, UITextViewDelegate {
    var parent: AttributedText

    init(_ view: AttributedText) {
      parent = view
    }

    func textView(_ textView: UITextView, shouldInteractWith URL: URL, in characterRange: NSRange, interaction: UITextItemInteraction) -> Bool {
      parent.linkPressed(URL)
      return false
    }
  }

  let content: NSAttributedString
  @Binding var height: CGFloat
  var linkPressed: (URL) -> Void

  public func makeUIView(context: Context) -> UITextView {
    let textView = UITextView()
    textView.backgroundColor = .clear
    textView.isEditable = false
    textView.isUserInteractionEnabled = true
    textView.delegate = context.coordinator
    textView.isScrollEnabled = false
    textView.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
    textView.dataDetectorTypes = .link
    textView.textContainerInset = .zero
    textView.textContainer.lineFragmentPadding = 0
    return textView
  }

  public func updateUIView(_ view: UITextView, context: Context) {
    view.attributedText = content

    // Compute the desired height for the content
    let fixedWidth = view.frame.size.width
    let newSize = view.sizeThatFits(CGSize(width: fixedWidth, height: CGFloat.greatestFiniteMagnitude))

    DispatchQueue.main.async {
      self.height = newSize.height
    }
  }

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


struct ContentView: View {

  private var text: NSAttributedString {
    NSAttributedString(string: "Eartheart is the principal settlement for the Gold Dwarves in East Rift and it is still the cultural and spiritual center for its people. Dwarves take on pilgrimages to behold the great holy city and take their trips from other countries and the deeps to reach their goal, it use to house great temples and shrines to all the Dwarven pantheon and dwarf heroes but after the great collapse much was lost.\n\nThe lords of their old homes relocated here as well the Deep Lords. The old ways of the Deep Lords are still the same as they use intermediaries and masking themselves to undermine the attempts of assassins or drow infiltrators. The Gold Dwarves outnumber every other race in the city and therefor have full control of the city and it's communities.")
  }

  @State private var height: CGFloat = .zero

  var body: some View {
    NavigationView {
      List {
        AttributedText(content: text, height: $height, linkPressed: { url in print(url) })
          .frame(height: height)

        Text("Hello world")
      }
      .listStyle(GroupedListStyle())
      .navigationBarTitle(Text("Content"), displayMode: .inline)
    }
  }
}

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

运行此代码时，您将看到AttributedText单元格太小而无法容纳其内容。

当您从navigationBarTitle删除displayMode: .inline参数时，它显示正常。

但是，如果我添加另一行来显示高度值（ Text("\\(height)") ），它会再次中断。

也许这是通过状态更改的视图更新触发的某种竞争条件？ height值本身是正确的，只是框架实际上没有那么高。 有解决方法吗？

将ScrollView与VStack一起使用确实解决了问题，但由于内容在实际应用程序中的显示方式，我真的更喜欢使用List 。

Answer 1

如果您不更改文本，即使没有绑定，您也可以计算宽度和高度并将它们用作框架。

List {
        // you don't need binding height
        AttributedText(content: text, linkPressed: { url in print(url) })
          .frame(height: frameSize(for: text).height)

        Text("Hello world")
      }

func frameSize(for text: String, maxWidth: CGFloat? = nil, maxHeight: CGFloat? = nil) -> CGSize {
        let attributes: [NSAttributedString.Key: Any] = [
            .font: UIFont.preferredFont(forTextStyle: .body)
        ]
        let attributedText = NSAttributedString(string: text, attributes: attributes)
        let width = maxWidth != nil ? min(maxWidth!, CGFloat.greatestFiniteMagnitude) : CGFloat.greatestFiniteMagnitude
        let height = maxHeight != nil ? min(maxHeight!, CGFloat.greatestFiniteMagnitude) : CGFloat.greatestFiniteMagnitude
        let constraintBox = CGSize(width: width, height: height)
        let rect = attributedText.boundingRect(with: constraintBox, options: [.usesLineFragmentOrigin, .usesFontLeading], context: nil).integral
        return rect.size
    }

带扩展：

extension String {
    func frameSize(maxWidth: CGFloat? = nil, maxHeight: CGFloat? = nil) -> CGSize {
        let attributes: [NSAttributedString.Key: Any] = [
            .font: UIFont.preferredFont(forTextStyle: .body)
        ]
        let attributedText = NSAttributedString(string: self, attributes: attributes)
        let width = maxWidth != nil ? min(maxWidth!, CGFloat.greatestFiniteMagnitude) : CGFloat.greatestFiniteMagnitude
        let height = maxHeight != nil ? min(maxHeight!, CGFloat.greatestFiniteMagnitude) : CGFloat.greatestFiniteMagnitude
        let constraintBox = CGSize(width: width, height: height)
        let rect = attributedText.boundingRect(with: constraintBox, options: [.usesLineFragmentOrigin, .usesFontLeading], context: nil).integral
        return rect.size
    }
}

Answer 2

所以我有这个确切的问题。

解决方案并不漂亮，但我找到了一个有效的解决方案：

首先，您需要继承 UITextView 以便您可以将其内容大小传递回 SwiftIU：

public class UITextViewWithSize: UITextView {
    @Binding var size: CGSize
    
    public init(size: Binding<CGSize>) {
        self._size = size
        
        super.init(frame: .zero, textContainer: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    public override func layoutSubviews() {
        super.layoutSubviews()
        self.size = sizeThatFits(.init(width: frame.width, height: 0))
    }
}

完成此操作后，您需要为自定义 UITextView 创建一个 UIViewRepresentable：

public struct HyperlinkTextView: UIViewRepresentable {
    public typealias UIViewType = UITextViewWithSize
    
    private var text: String
    private var font: UIFont?
    private var foreground: UIColor?
    @Binding private var size: CGSize
    
    public init(_ text: String, font: UIFont? = nil, foreground: UIColor? = nil, size: Binding<CGSize>) {
        self.text = text
        self.font = font
        self.foreground = foreground
        self._size = size
    }
    
    public func makeUIView(context: Context) -> UIViewType {
        
        let view = UITextViewWithSize(size: $size)
        
        view.isEditable = false
        view.dataDetectorTypes = .all
        view.isScrollEnabled = false
        view.text = text
        view.textContainer.lineBreakMode = .byTruncatingTail
        view.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        view.setContentCompressionResistancePriority(.required, for: .vertical)
        view.textContainerInset = .zero
        
        if let font = font {
            view.font = font
        } else {
            view.font = UIFont.preferredFont(forTextStyle: .body)
        }
        
        if let foreground = foreground {
            view.textColor = foreground
        }
        
        view.sizeToFit()
        
        return view
    }
    
    public func updateUIView(_ uiView: UIViewType, context: Context) {
        uiView.text = text
        uiView.layoutSubviews()
    }
}

现在我们可以轻松访问视图的内容大小，我们可以使用它来强制视图适合该大小的容器。 出于某种原因，仅仅在视图上使用 .frame 是行不通的。 该视图只是忽略其给定的框架。 但是当把它放入几何阅读器时，它似乎按预期增长。

GeometryReader { proxy in
    HyperlinkTextView(bio, size: $bioSize)
        .frame(maxWidth: proxy.frame(in: .local).width, maxHeight: .infinity)
}
.frame(height: bioSize.height)

Answer 3

我设法找到了一个最有效的AttributedText视图版本。

struct AttributedText: UIViewRepresentable {
  class HeightUITextView: UITextView {
    @Binding var height: CGFloat

    init(height: Binding<CGFloat>) {
      _height = height
      super.init(frame: .zero, textContainer: nil)
    }

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

    override func layoutSubviews() {
      super.layoutSubviews()
      let newSize = sizeThatFits(CGSize(width: frame.size.width, height: CGFloat.greatestFiniteMagnitude))
      if height != newSize.height {
        height = newSize.height
      }
    }
  }

  class Coordinator: NSObject, UITextViewDelegate {
    var parent: AttributedText

    init(_ view: AttributedText) {
      parent = view
    }

    func textView(_ textView: UITextView, shouldInteractWith URL: URL, in characterRange: NSRange, interaction: UITextItemInteraction) -> Bool {
      parent.linkPressed(URL)
      return false
    }
  }

  let content: NSAttributedString
  @Binding var height: CGFloat
  var linkPressed: (URL) -> Void

  public func makeUIView(context: Context) -> UITextView {
    let textView = HeightUITextView(height: $height)
    textView.attributedText = content
    textView.backgroundColor = .clear
    textView.isEditable = false
    textView.isUserInteractionEnabled = true
    textView.delegate = context.coordinator
    textView.isScrollEnabled = false
    textView.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
    textView.dataDetectorTypes = .link
    textView.textContainerInset = .zero
    textView.textContainer.lineFragmentPadding = 0
    return textView
  }

  public func updateUIView(_ textView: UITextView, context: Context) {
    if textView.attributedText != content {
      textView.attributedText = content

      // Compute the desired height for the content
      let fixedWidth = textView.frame.size.width
      let newSize = textView.sizeThatFits(CGSize(width: fixedWidth, height: CGFloat.greatestFiniteMagnitude))

      DispatchQueue.main.async {
        self.height = newSize.height
      }
    }
  }

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

在某些情况下，您可以看到视图的大小突然变大，但在我使用它的几乎所有屏幕中，这是一个巨大的改进。 尽管如此，在 SwiftUI 中自动调整 UITextView 的大小仍然是一个令人头疼的问题，任何可以改善这一点的答案都将不胜感激:)

Answer 4

要获取 UIViewRepresentable View 的高度，将其放置在具有相同高度的文本的背景中。

  private let text: String = "Eartheart is the principal settlement for the Gold Dwarves in East Rift and it is still the cultural and spiritual center for its people. Dwarves take on pilgrimages to behold the great holy city and take their trips from other countries and the deeps to reach their goal, it use to house great temples and shrines to all the Dwarven pantheon and dwarf heroes but after the great collapse much was lost.\n\nThe lords of their old homes relocated here as well the Deep Lords. The old ways of the Deep Lords are still the same as they use intermediaries and masking themselves to undermine the attempts of assassins or drow infiltrators. The Gold Dwarves outnumber every other race in the city and therefor have full control of the city and it's communities."


...

            Text(text)
                .font(.system(size: 12))
                .fixedSize(horizontal: false, vertical: true)
                .opacity(0)
                .background(
                    CustomUIViewRepresentableTextView(text: text)
                    // same font size 
                )

Answer 5

我最近将我们的应用程序中的一些代码重构为 SwiftUI，并且还发现了一些明显在 Stackoverflow 上发现的类似方法。 经过一些研究、尝试和错误，我最终得到了一个非常简单的解决方案，它完全符合我们的目的：

• 支持属性字符串的 SwiftUI 文本组件
• 支持 HTML 和可点击链接
• 自动调整高度并且在 UITextView 中没有滚动
• 支持 iOS 13.0+
• 使用方便
• （可选）不可选择

    import UIKit
    import SwiftUI
    
    protocol StringFormatter {
        func format(string: String) -> NSAttributedString?
    }
    
    struct AttributedText: UIViewRepresentable {
        typealias UIViewType = UITextView
        
        @State
        private var attributedText: NSAttributedString?
        private let text: String
        private let formatter: StringFormatter
        private var delegate: UITextViewDelegate?
        
        init(_ text: String, _ formatter: StringFormatter, delegate: UITextViewDelegate? = nil) {
            self.text = text
            self.formatter = formatter
            self.delegate = delegate
        }
        
        func makeUIView(context: Context) -> UIViewType {
            let view = ContentTextView()
            view.setContentHuggingPriority(.required, for: .vertical)
            view.setContentHuggingPriority(.required, for: .horizontal)
            view.contentInset = .zero
            view.textContainer.lineFragmentPadding = 0
            view.delegate = delegate
            return view
        }
        
        func updateUIView(_ uiView: UITextView, context: Context) {
            guard let attributedText = attributedText else {
                generateAttributedText()
                return
            }
            
            uiView.attributedText = attributedText
        }
        
        private func generateAttributedText() {
            guard attributedText == nil else { return }
            // create attributedText on main thread since HTML formatter will crash SwiftUI
            DispatchQueue.main.async {
                self.attributedText = self.formatter.format(string: self.text)
            }
        }
        
        /// ContentTextView
        /// subclass of UITextView returning contentSize as intrinsicContentSize
        private class ContentTextView: UITextView {
            override var canBecomeFirstResponder: Bool { false }
            
            override var intrinsicContentSize: CGSize {
                frame.height > 0 ? contentSize : super.intrinsicContentSize
            }
        }
    }

格式化程序

    import Foundation
    
    class HTMLFormatter: StringFormatter {
        func format(string: String) -> NSAttributedString? {
            guard let data = string.data(using: .utf8),
                  let attributedText = try? NSAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue], documentAttributes: nil)
            else { return nil }
            
            return attributedText
        }
    }

样本

    import SwiftUI
    
    struct AttributedTextListView: View {
        let html = """
                    <html>
                        <body>
                            <h1>Hello, world!</h1>
                            <span>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</span>
                            <a href="https://example.org">Example</a>
                        </body>
                    </html>
                    """
        var body: some View {
            List {
                Group {
                    // delegate is optional
                    AttributedText(html, HTMLFormatter(), delegate: nil)
                    AttributedText(html, HTMLFormatter(), delegate: nil)
                    AttributedText(html, HTMLFormatter(), delegate: nil)
                }.background(Color.gray.opacity(0.1))
            }
            
        }
    }