由于官方允许并记录了到 UIKit 的桥梁，因此可以在需要时从那里读取所需的信息.

As bridge to UIKit is officially allowed and documented, it is possible to read needed information from there when needed.

这是直接从 UITabBar

// Helper bridge to UIViewController to access enclosing UITabBarController
// and thus its UITabBar
struct TabBarAccessor: UIViewControllerRepresentable {
    var callback: (UITabBar) -> Void
    private let proxyController = ViewController()

    func makeUIViewController(context: UIViewControllerRepresentableContext<TabBarAccessor>) ->
                              UIViewController {
        proxyController.callback = callback
        return proxyController
    }

    func updateUIViewController(_ uiViewController: UIViewController, context: UIViewControllerRepresentableContext<TabBarAccessor>) {
    }

    typealias UIViewControllerType = UIViewController

    private class ViewController: UIViewController {
        var callback: (UITabBar) -> Void = { _ in }

        override func viewWillAppear(_ animated: Bool) {
            super.viewWillAppear(animated)
            if let tabBar = self.tabBarController {
                self.callback(tabBar.tabBar)
            }
        }
    }
}

// Demo SwiftUI view of usage
struct TestTabBar: View {
    var body: some View {
        TabView {
            Text("First View")
                .background(TabBarAccessor { tabBar in
                    print(">> TabBar height: (tabBar.bounds.height)")
                    // !! use as needed, in calculations, @State, etc.
                })
                .tabItem { Image(systemName: "1.circle") }
                .tag(0)
            Text("Second View")
                .tabItem { Image(systemName: "2.circle") }
                .tag(1)
        }
    }
}