在 SwiftUI 中通过摇动手势（使用 UIKit）设置 EnvironmentObject 不会更新视图

Question

我希望通过物理摇动设备来触发 SwiftUI 功能。 由于此时运动检测不是 SwiftUI 的功能，我需要使用 UIKit 集成和协调器返回一个 Bool 值，该值将指示设备已被摇晃，从而触发 SwiftUI 功能。

以下代码在识别设备晃动方面效果很好（这一点由单独的“makeShakerSound()”函数证明，该函数在晃动时播放声音片段并且效果很好）。 除了识别晃动的工作代码之外，我还包含了用于从 ContentView 调用 ShakableViewRepresentable(isShaken: $shakeOccurred) 的代码，如下所示。

我创建了一个 EnvironmentObject 来标记设备已被摇晃，并使用 objectWillChange 来宣布发生了更改。

我的问题是：当检测到摇晃动作时，摇晃声音效果很好，但是我的 ContentView 没有针对环境对象 myDevice.isShaken 的变化而更新。 我认为使用 objectWillChange 可能会解决这个问题，但事实并非如此。 我错过了什么？

我很抱歉 - 我对此有点陌生。

/* CREATE AN ENVIRONMENTAL OBJECT TO INDICATE DEVICE HAS BEEN SHAKEN */

import Combine
import SwiftUI

class MyDevice: ObservableObject {
    // let objectWillChange = ObservableObjectPublisher()
    var isShaken: Bool = false {
        willSet {
            self.objectWillChange.send()
        }
    }
}


/* DETECT SHAKE GESTURE AND FLAG THAT SHAKING HAS OCCURRED */

import UIKit
import SwiftUI

struct ShakableViewRepresentable: UIViewControllerRepresentable {

    class Coordinator: NSObject {
        var parent: ShakableViewRepresentable
        init(_ parent: ShakableViewRepresentable) {
            self.parent = parent
        }
    }

    func makeCoordinator() -> ShakableViewRepresentable.Coordinator {
        Coordinator(self)
    }

    func makeUIViewController(context: Context) -> ShakableViewController {
        ShakableViewController()
    }
    func updateUIViewController(_ uiViewController: ShakableViewController, context: Context) {}
}

class ShakableViewController: UIViewController {

    override func motionBegan(_ motion: UIEvent.EventSubtype, with event: UIEvent?) {
        guard motion == .motionShake else { return }

         /* SHAKING GESTURE WAS DETECTED */
        myDevice?.isShaken = true       /* ContentView doesn't update! */
        makeShakerSound()       /* This works great */

        /* I’M TRYING TO TRIGGER A FUNCTION IN SWIFTUI BY SHAKING THE DEVICE:  Despite setting the myDevice.isShaken environment object to "true", my ContentView doesn't update when the shaking gesture is detected.   */

    }
}


ContentView.swift

    @EnvironmentObject var myDevice: MyDevice

    var body: some View {
        NavigationView {

            ZStack {

                /* DETECT SHAKE GESTURE - This works */
                ShakableViewRepresentable()
                    .allowsHitTesting(false)

                VStack {
                    /* SHOW CURRENT STATE OF myDevice.isShaken - Doesn't update */
                    Text(self.myDevice.isShaken ? "The device has been shaken" : "No shaking has occurred")
                    Text("Device was shaken: \(self.myDevice.isShaken.description)")
                }

/* more views below */

Answer 1

例子

import SwiftUI
import Combine

class MyDevice: ObservableObject {
    //let objectWillChange = ObservableObjectPublisher()
    var isShaken: Bool = false {
        willSet {
            self.objectWillChange.send()
        }
    }
}
struct ContentView: View {
    @ObservedObject var model = MyDevice()
    var body: some View {
        VStack {
            Text("\(model.isShaken.description)").onTapGesture {
                self.model.isShaken.toggle()
            }

        }
    }
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

只需取消注释该行

let objectWillChange = ObservableObjectPublisher()

它停止工作。

不要重新定义你自己的 ObservableObjectPublisher()

已检查

import SwiftUI
import Combine

class MyDevice: ObservableObject {
    //let objectWillChange = ObservableObjectPublisher()
    var isShaken: Bool = false {
        willSet {
            self.objectWillChange.send()
        }
    }
}
struct ContentView: View {
    @EnvironmentObject var model: MyDevice
    var body: some View {
        VStack {
            Text("\(model.isShaken.description)").onTapGesture {
                self.model.isShaken.toggle()
            }

        }
    }
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView().environmentObject(MyDevice())
    }
}

在 SceneDelegate.swift 中

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).

        // Create the SwiftUI view that provides the window contents.
        let contentView = ContentView().environmentObject(MyDevice())
        //let contentView = ContentView()

        // Use a UIHostingController as window root view controller.
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: contentView)
            self.window = window
            window.makeKeyAndVisible()
        }
    }

它按预期工作。

好的，用你的抖动检测器，

myDevice?.isShaken = true

永远不会运行，只是因为 myDevice 为零

解决方案

使您的模型全局可用，因为在 SwiftUI 中我们没有工具如何使其可用于 ShakableViewController，或将其用作其 init 的参数

SwiftDelegate.swift

import UIKit
import SwiftUI

let model = MyDevice()

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?


    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).

        // Create the SwiftUI view that provides the window contents.
        let contentView = ContentView().environmentObject(model)
        //let contentView = ContentView()

        // Use a UIHostingController as window root view controller.
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: contentView)
            self.window = window
            window.makeKeyAndVisible()
        }
    }

    func sceneDidDisconnect(_ scene: UIScene) {
        // Called as the scene is being released by the system.
        // This occurs shortly after the scene enters the background, or when its session is discarded.
        // Release any resources associated with this scene that can be re-created the next time the scene connects.
        // The scene may re-connect later, as its session was not neccessarily discarded (see `application:didDiscardSceneSessions` instead).
    }

    func sceneDidBecomeActive(_ scene: UIScene) {
        // Called when the scene has moved from an inactive state to an active state.
        // Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
    }

    func sceneWillResignActive(_ scene: UIScene) {
        // Called when the scene will move from an active state to an inactive state.
        // This may occur due to temporary interruptions (ex. an incoming phone call).
    }

    func sceneWillEnterForeground(_ scene: UIScene) {
        // Called as the scene transitions from the background to the foreground.
        // Use this method to undo the changes made on entering the background.
    }

    func sceneDidEnterBackground(_ scene: UIScene) {
        // Called as the scene transitions from the foreground to the background.
        // Use this method to save data, release shared resources, and store enough scene-specific state information
        // to restore the scene back to its current state.
    }


}

内容视图.swift

import SwiftUI
import Combine

struct ShakableViewRepresentable: UIViewControllerRepresentable {

    class Coordinator: NSObject {
        var parent: ShakableViewRepresentable
        init(_ parent: ShakableViewRepresentable) {
            self.parent = parent
        }
    }

    func makeCoordinator() -> ShakableViewRepresentable.Coordinator {
        Coordinator(self)
    }

    func makeUIViewController(context: Context) -> ShakableViewController {
        ShakableViewController()
    }
    func updateUIViewController(_ uiViewController: ShakableViewController, context: Context) {}
}

class ShakableViewController: UIViewController {
    override func motionBegan(_ motion: UIEvent.EventSubtype, with event: UIEvent?) {
        guard motion == .motionShake else { return }

        model.isShaken.toggle()
        print(model.isShaken)


    }
}


class MyDevice: ObservableObject {
    //let objectWillChange = ObservableObjectPublisher()
    var isShaken: Bool = false {
        willSet {
            self.objectWillChange.send()
        }
    }
}
struct ContentView: View {
    @EnvironmentObject var model: MyDevice
    var body: some View {
        VStack {
            ShakableViewRepresentable()
                               .allowsHitTesting(false)
            Text(self.model.isShaken ? "The device has been shaken" : "No shaking has occurred").onTapGesture {
                self.model.isShaken.toggle()
            }

        }
    }
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView().environmentObject(MyDevice())
    }
}

它的工作原理，至少在我的设备上:-)

没有声音，但它打印

true
false
true
false
true

每一次摇晃客人