UIKit混编时Dismiss掉HostController

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UIKit混编时Dismiss掉HostController

2021-08-07

2026-10-12

SwiftUI

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场景：在主UIKit的项目中Present出一个包含SwiftUI的UIHostingController 当需要Dismiss该控制器的时候遇到了麻烦

一：在SwiftUI中Dismiss一个页面的正常操作#

下面的实现方式在正常的SwiftUI体系下是可以正常工作的但是在UIKit混编时就失效了

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struct ContentView: View, SwiftUIBridgeProtocol {
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    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
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    var body: some View {
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        ZStack {
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            VStack {
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                StoreTopView(dismissClosure: {
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                    presentationMode.wrappedValue.dismiss()
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                })
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                .padding()
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            }
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        }
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    }
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}

我们看下打印的信息：

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(lldb) po presentationMode
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▿ Binding<PresentationMode>
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  ▿ transaction : Transaction
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    ▿ plist : []
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      - elements : nil
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  ▿ location : <LocationBox<FunctionalLocation<PresentationMode>>: 0x2838313c0>
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  ▿ _value : PresentationMode
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    - isPresented : false
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(lldb) po presentationMode.wrappedValue
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▿ PresentationMode
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  - isPresented : false

二：如何才能获取到`HostController`呢#

方案1. 一些方案#

下面的文正提供了一些尝试的方案，但不够SwiftUI风格

Controlling UIHostingController with SwiftUI View

方案2.@Environment#

通过一段时间的SwiftUI学习，发现通过@Environment可以获取到很多当前页面的一些有用信息。但是通过观察可用的字段并没有发现有关HostController的线索。

那是否可以添加自定义字段呢？#

可以！查看EnvironmentKey相关的文档或者注释我们可以发现，其中已经提供了自定义的示例代码：

You can create custom environment values by extending the EnvironmentValues structure with new properties. First declare a new environment key type and specify a value for the required defaultValue property:

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private struct MyEnvironmentKey: EnvironmentKey {
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    static let defaultValue: String = "Default value"
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}

The Swift compiler automatically infers the associated Value type as the type you specify for the default value. Then use the key to define a new environment value property:

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extension EnvironmentValues {
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    var myCustomValue: String {
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        get { self[MyEnvironmentKey.self] }
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        set { self[MyEnvironmentKey.self] = newValue }
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    }
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}

Clients of your environment value never use the key directly. Instead, they use the key path of your custom environment value property. To set the environment value for a view and all its subviews, add the environment(::) view modifier to that view:

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MyView()
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    .environment(\.myCustomValue, "Another string")

As a convenience, you can also define a dedicated view modifier to apply this environment value:

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extension View {
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    func myCustomValue(_ myCustomValue: String) -> some View {
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        environment(\.myCustomValue, myCustomValue)
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    }
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}

This improves clarity at the call site:

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MyView()
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    .myCustomValue("Another string")

To read the value from inside MyView or one of its descendants, use the Environment property wrapper:

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struct MyView: View {
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    @Environment(\.myCustomValue) var customValue: String
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    var body: some View {
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        Text(customValue) // Displays "Another value".
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    }
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}

三：下面按照上面的思路实现一下#

3.1 用以承载`ViewController`的容器#

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public struct ViewControllerHolder {
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    public weak var value: UIViewController?
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    init(_ value: UIViewController?) {
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        self.value = value
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    }
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}

3.2 EnvironmentKey#

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public struct ViewControllerKey: EnvironmentKey {
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    public static var defaultValue: ViewControllerHolder { return ViewControllerHolder(nil) }
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}

3.3 Extension#

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extension EnvironmentValues {
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    public var viewController: ViewControllerHolder {
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        get { return self[ViewControllerKey.self] }
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        set { self[ViewControllerKey.self] = newValue }
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    }
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}

3.4 打开页面#

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extension UIViewController {
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    public func present<Content: View>(presentationStyle: UIModalPresentationStyle = .automatic, transitionStyle: UIModalTransitionStyle = .coverVertical, animated: Bool = true, completion: @escaping () -> Void = {}, @ViewBuilder builder: () -> Content) {
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        let toPresent = UIHostingController(rootView: AnyView(EmptyView()))
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        toPresent.modalPresentationStyle = presentationStyle
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        toPresent.rootView = AnyView(
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            builder()
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                .environment(\.viewController, ViewControllerHolder(toPresent))
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        )
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        if presentationStyle == .overCurrentContext {
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            toPresent.view.backgroundColor = .clear
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        }
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        self.present(toPresent, animated: animated, completion: completion)
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    }
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}

3.5 关闭页面#

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struct ShopContentView: View {
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...
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    // MARK: - Body
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    var body: some View {
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        ZStack(alignment: .top) {
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            ...
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            viewControllerHolder.value?.dismiss(animated: false, completion: nil)
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            ...
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        })
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    }
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...
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    // MARK: -  Var: Environment
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    @Environment(\.viewController) var viewControllerHolder
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...
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}