SwiftUI NavigationBar 高度

Question

如何获取当前NavigationBar的高度？在 UIKit 中我们可以得到

navigationController?.navigationBar.frame.height

但找不到 SwiftUI 的任何内容...

Answer 1

基于此post（感谢Asperi):

struct NavBarAccessor: UIViewControllerRepresentable {
    var callback: (UINavigationBar) -> Void
    private let proxyController = ViewController()

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

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

    typealias UIViewControllerType = UIViewController

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

        override func viewWillAppear(_ animated: Bool) {
            super.viewWillAppear(animated)
            if let navBar = self.navigationController {
                self.callback(navBar.navigationBar)
            }
        }
    }
}

然后我们可以从任何视图调用它：

.background(NavBarAccessor { navBar in
      print(">> NavBar height: \(navBar.bounds.height)")
                // !! use as needed, in calculations, @State, etc.
 })

Answer 2

基于@yoprst 的响应，而不是配置计算和@State 变量，您还可以return View 直接插入到层次结构中：

struct NavigationBarAccessor: UIViewControllerRepresentable {
    var callback: (UINavigationBar) -> (AnyView)
    private let proxyViewController = ProxyViewController()

    func makeUIViewController(context: UIViewControllerRepresentableContext<NavigationBarAccessor>) -> UIViewController {
        self.proxyViewController.callback = callback
        return proxyViewController
    }

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

    private class ProxyViewController: UIViewController {
        var callback: ((UINavigationBar) -> AnyView)?

        override func viewWillAppear(_ animated: Bool) {
            super.viewWillAppear(animated)
            if let navigationBar = self.navigationController?.navigationBar {
                _ = self.callback?(navigationBar)
            }
        }
    }
}

用法：

VStack {
    NavigationBarAccessor { navigationBar in
        Spacer()
            .frame(height: navigationBar.frame.height)
    }
}

SwiftUI NavigationBar 高度

SwiftUI NavigationBar height

height

swiftui

navigationbar