ios - UIKit 中的可扩展 SwiftUI View 垂直居中

Question

我在 UIKit 应用程序中集成了一些新的 SwiftUI View ，但遇到了问题。我已经研究了以下问题很长一段时间，但尚未找到原因和解决方案。该问题具体发生在将View集成到UIKit中时。我正在尝试创建一个简单的可点击 View ，在点击时垂直展开/折叠。

这就是 SwiftUI View 预览的样子(以及它应该如何表现):
Screenshot
Video

这是我在 UIKit 中实现 SwiftUI View 时得到的结果:
Screenshot
Video

似乎即使我将 UIHostingController View 的顶部操作限制为父 View ，UIHostingController View 也会垂直居中。

如评论中所述，我可以将 HostController View 的底部限制在其父 View 的底部，但这会使下面的内容无法交互。

我正在寻找的是 HostController View 约束(特别是高度)与 SwiftUI View 框架匹配的解决方案。

SwiftUI View 的代码:

import SwiftUI

struct ColorView: View {
  @State var isCollapsed = true

  var body: some View {
    VStack {
      VStack(spacing: 5) {
        HStack {
          Spacer()
          Text("Title")
          Spacer()
        }
        .frame(height: 100)

        if !isCollapsed {
          HStack {
            Spacer()
            Text("description")
            Spacer()
          }
          .padding(40)
        }
      }
      .background(Color(isCollapsed ? UIColor.red : UIColor.blue))
      .onTapGesture {
        withAnimation {
          self.isCollapsed.toggle()
        }
      }

      Spacer()
    }
  }
}

struct ColorView_Previews: PreviewProvider {
  static var previews: some View {
    return ColorView()
  }
}

以及上述SwiftUI View的ViewController中的UIKit实现:

struct ViewControllerRepresentable: UIViewControllerRepresentable {
  typealias UIViewControllerType = ViewController

  func makeUIViewController(context: UIViewControllerRepresentableContext<ViewControllerRepresentable>) -> ViewControllerRepresentable.UIViewControllerType {
    return ViewController()
  }

  func updateUIViewController(_ uiViewController: ViewControllerRepresentable.UIViewControllerType, context: UIViewControllerRepresentableContext<ViewControllerRepresentable>) { }
}

class ViewController: UIViewController {
  override func viewDidLoad() {
    super.viewDidLoad()

    let colorView = ColorView()
    let colorController = UIHostingController(rootView: colorView)

    addChild(colorController)
    view.addSubview(colorController.view)
    colorController.didMove(toParent: self)

    colorController.view.translatesAutoresizingMaskIntoConstraints = false
    colorController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
    colorController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
    colorController.view.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
  }
}

struct ViewControllerRepresentable_Previews: PreviewProvider {
  static var previews: some View {
    Group {
      ViewControllerRepresentable()
    }
  }
}

非常感谢任何帮助。

Answer 1

这是在 iOS Single View Playground (Xcode 11.2) 中测试过的代码快照。原始的 ColorView 没有改变，所以下面没有重复。

UIKit UIViewController 中集成 SwiftUI View 的行为与纯 SwiftUI 环境中的行为相同。

import UIKit
import PlaygroundSupport
import SwiftUI

class MyViewController : UIViewController {
    override func loadView() {
        let view = UIView()
        view.backgroundColor = .white
        self.view = view
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        let child = UIHostingController(rootView: ColorView())
        addChild(child)
        self.view.addSubview(child.view)
        child.didMove(toParent: self)

        child.view.translatesAutoresizingMaskIntoConstraints = false
        child.view.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        child.view.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        child.view.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        child.view.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
    }
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()