swift - 带有 SwiftUI 内容的 UITableViewHeaderFooterView 自动插入安全区域

Question

我有一个基本的 UITableView与一些细胞。我正在使用 SwiftUI View作为我的单元格和节标题的内容。奇怪的是，只有在 iPhone XS Max 上似乎触碰屏幕底部的部分标题似乎得到了 rawSafeAreaInset 16pts(检查调试 View 层次结构)。我的细胞按预期工作。

为了看看发生了什么，我在 contentView 中添加了一个虚拟的蓝色 SwiftUI 矩形。 ，然后在顶部放置一个红色的 UIView，两个 View 都设置为相同的约束。 UITableView已设置为对标题和单元格使用自动尺寸。

public class SectionHeader: UITableViewHeaderFooterView {
  public static let reusableIdentifier = "Section"

  private var innerHostedViewController: UIHostingController<AnyView>!

  public override init(reuseIdentifier: String?) {
    super.init(reuseIdentifier: reuseIdentifier)

    setupHeader()
  }

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

  private func setupHeader() {
    self.backgroundView = UIView()
    self.backgroundView?.backgroundColor = UIColor.green.withAlphaComponent(0.2)

    innerHostedViewController = UIHostingController(rootView: AnyView(Rectangle().fill(Color.blue).frame(height: 48)))
    innerHostedViewController.view.translatesAutoresizingMaskIntoConstraints = false
    innerHostedViewController.view.frame = self.contentView.bounds
    contentView.addSubview(innerHostedViewController.view)
    innerHostedViewController.view.backgroundColor = .clear

    let vv = UIView()
    vv.translatesAutoresizingMaskIntoConstraints = false
    vv.backgroundColor = .red
    contentView.addSubview(vv)

    NSLayoutConstraint.activate([
      vv.topAnchor.constraint(equalTo: self.contentView.topAnchor),
      vv.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor),
      vv.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor),
      vv.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor),

      innerHostedViewController.view.topAnchor.constraint(equalTo: self.contentView.topAnchor),
      innerHostedViewController.view.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor),
      innerHostedViewController.view.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor),
      innerHostedViewController.view.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor),
    ])
  }
}

正如您在下图中所看到的，顶部两个标题(带有空单元格用于演示)可见红色叠加层，但屏幕上的最后一个蓝色 SwiftUI 矩形向上移动!



这个 SwiftUI View 似乎以某种方式获得了一些 safeAreaInset，并且似乎没有办法关闭它。如果向上滚动，插图也不会消失。它永远留在那里。我尝试关闭 SwiftUI View 的安全区域插图，但这也无济于事:

innerHostedViewController = UIHostingController(rootView: AnyView(Rectangle().fill(Color.blue).frame(height: 48).edgesIgnoringSafeArea(.all)))

我如何摆脱这个插图？正如我提到的 - 它只发生在 UITableViewHeaderFooterView s 而不是 UITableViewCell s。

调试 View 层次结构揭示了基于安全区域插图的虚假底部填充修饰符:

Answer 1

在这个子类中托管 View UIHostingController为我做的伎俩!

/// https://twitter.com/b3ll/status/1193747288302075906
class FixSafeAreaInsetsHostingViewController<Content: SwiftUI.View>: UIHostingController<Content> {
    func fixApplied() -> Self {
        self.fixSafeAreaInsets()
        return self
    }

    func fixSafeAreaInsets() {
        guard let _class = view?.classForCoder else {
            fatalError()
        }

        let safeAreaInsets: @convention(block) (AnyObject) -> UIEdgeInsets = { (sself: AnyObject!) -> UIEdgeInsets in
            return .zero
        }
        guard let method = class_getInstanceMethod(_class.self, #selector(getter: UIView.safeAreaInsets)) else { return }
        class_replaceMethod(_class, #selector(getter: UIView.safeAreaInsets), imp_implementationWithBlock(safeAreaInsets), method_getTypeEncoding(method))

        let safeAreaLayoutGuide: @convention(block) (AnyObject) -> UILayoutGuide? = { (sself : AnyObject!) -> UILayoutGuide? in return nil }

        guard let method2 = class_getInstanceMethod(_class.self, #selector(getter: UIView.safeAreaLayoutGuide)) else { return }
        class_replaceMethod(_class, #selector(getter: UIView.safeAreaLayoutGuide), imp_implementationWithBlock(safeAreaLayoutGuide), method_getTypeEncoding(method2))
    }

    override var prefersStatusBarHidden: Bool {
        return false
    }
}