SwiftUI 不活动计时器-解网

问：

我想在用户 30 秒未触摸屏幕后显示提示。为此，每当触摸屏幕时都需要调用此函数。restartInactivityTimer()

有没有办法发现任何屏幕触摸来重新启动计时器，但没有“消耗”它的点击手势？我真的需要从每个 onTapGesture（子）视图闭包进行调用，就像下面的代码片段一样吗？restartInactivityTimer()

struct MyView: View {
    @State private var inactivityTimer: Timer?

    var body: some View {
        VStack { 
            subView1
            subView2
            subView3
            subView4
        }
        .onAppear {
            restartInactivityTimer()
        }
        .onTapGesture {
            // not reaching here when any subView is touched
            restartInactivityTimer() 
        }
    }

    func restartInactivityTimer() {
        inactivityTimer?.invalidate()
        inactivityTimer = Timer.scheduledTimer(withTimeInterval: 30.0, repeats: false) { _ in
            showHint()
        }
    }

    var subView1: some View {
        // ...
        .onTapGesture {
            // ... other actions for tapping that subview
            restartInactivityTimer()
        }
    }

    // ... other subviews
}

SwiftUI 计时器触摸事件用户不活动

@main
struct EntryPoint {
    // swizzle here
    static func main() {
        let original = class_getInstanceMethod(UIApplication.self, #selector(UIApplication.sendEvent))!
        let new = class_getInstanceMethod(ActivityDetector.self, #selector(ActivityDetector.mySendEvent))!
        method_exchangeImplementations(original, new)

        // launch your app
        YourApp.main()
    }
    
}

struct YourApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

swizzled 方法是：

class ActivityDetector: NSObject {
    
    private typealias SendEventFunc = @convention(c) (AnyObject, Selector, UIEvent) -> Void
    
    @objc func mySendEvent(_ event: UIEvent) {
        // call the original sendEvent
        // from: https://stackoverflow.com/a/61523711/5133585
        unsafeBitCast(
            class_getMethodImplementation(ActivityDetector.self, #selector(mySendEvent)),
            to: SendEventFunc.self
        )(self, #selector(UIApplication.sendEvent), event)

        // send a notification, just like in the non-SwiftUI solutions
        NotificationCenter.default.post(name: .init("UserActivity"), object: nil)
    }
}

现在，在您的视图中，您可以收听通知：

@State var presentAlert = false
@State var timer = Timer.publish(every: 60, on: .current, in: .common).autoconnect()

var body: some View {
    Text("Foo")
        // time is up!
        .onReceive(timer) { _ in
            presentAlert = true
            timer.upstream.connect().cancel()
        }
        // user did something!
        .onReceive(NotificationCenter.default.publisher(for: .init("UserActivity")), perform: { _ in
            timer.upstream.connect().cancel()
            timer = Timer.publish (every: 5, on: .current, in: .common).autoconnect()
        })
        .alert("Foo", isPresented: $presentAlert) {
            Button("OK") {}
        }
}

使用 here 有点浪费，因为你只需要发布者的一个输出。例如，请考虑使用 a：Timer.publishTask

@State var presentAlert = false
@State var task: Task<Void, Error>?

var body: some View {
    Text("Foo")
        .onAppear {
            resetTask()
        }
        .onReceive(NotificationCenter.default.publisher(for: .init("UserActivity")), perform: { _ in
            task?.cancel()
            resetTask()
        })
        .alert("Foo", isPresented: $presentAlert) {
            Button("OK") {}
        }
}

@MainActor
func resetTask() {
    task = Task {
        try await Task.sleep(for: .seconds(60))
        try Task.checkCancellation()
        presentAlert = true
    }
}

SwiftUI 不活动计时器

SwiftUI inactivity timer

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