UIViewRepresentable 自动大小 - 将 UIKit UIView 大小传递给 SwiftUI

Question

假设你有一个 UIKit 视图想要决定它自己的大小（通过 intrinsicContentSize 或布局约束，大小可能会改变）。例如：

/// Some UIKit view that wants to have a specific size
class YellowBoxUIKitView : UIView {

    init() {
        super.init(frame: .zero)
        self.backgroundColor = .yellow
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) is not supported")
    }

    override var intrinsicContentSize: CGSize {
        return CGSize(width: 100, height: 100)
    }

}

如何将其包装为 SwiftUI UIViewRepresentable 并使其自动将 UIView 大小传递给 SwiftUI？

struct YellowBoxView : UIViewRepresentable {

    func makeUIView(context: Context) -> YellowBoxUIKitView {
        // TODO: How do you pass the size from UIKit up to SwiftUI?
        YellowBoxUIKitView()
    }

    func updateUIView(_ uiView: YellowBoxUIKitView, context: Context) {
    }

}

SwiftUI 不考虑 UIView 的大小，只是给它最大可能的宽度/高度。

可运行示例：SizedUIViewRepresentableView

这里有一个关于 UITextView 的类似问题：Update UIViewRepresentable size from UIKit in SwiftUI

Answer 1

解决方案是为表示的UIView 显式设置压缩/拥抱优先级

使用 Xcode 11.4 / iOS 13.4 测试

struct YellowBoxView : UIViewRepresentable {

    func makeUIView(context: Context) -> YellowBoxUIKitView {
        let view = YellowBoxUIKitView()

        view.setContentHuggingPriority(.required, for: .horizontal) // << here !!
        view.setContentHuggingPriority(.required, for: .vertical)

        // the same for compression if needed

        return view
    }

    func updateUIView(_ uiView: YellowBoxUIKitView, context: Context) {
    }
}