watchOS：使用 SwiftUI 进行 Apple Watch 开发的基础知识

import BackgroundTasks
import WatchKit

/// 在 watchOS 上规划后台数据更新
class BackgroundTaskManager: NSObject {

    func scheduleBackgroundRefresh() {
        let request = BGAppRefreshTaskRequest(identifier: "com.example.refresh")
        request.earliestBeginDate = Date(timeIntervalSinceNow: 30 * 60)

        try? BGTaskScheduler.shared.submit(request)
    }

    func handleAppRefresh(task: BGAppRefreshTask) {
        task.expirationHandler = { task.setTaskCompleted(success: false) }

        DataService.shared.fetchData { result in
            switch result {
            case .success:
                ComplicationController.reloadComplications()
                task.setTaskCompleted(success: true)
            case .failure:
                task.setTaskCompleted(success: false)
            }
        }
    }
}

/// 在 WKExtensionDelegate 中注册后台任务
class ExtensionDelegate: NSObject, WKExtensionDelegate {
    let manager = BackgroundTaskManager()

    func handle(_ backgroundTasks: Set<WKBackgroundTask>) {
        for task in backgroundTasks {
            switch task {
            case let refreshTask as BGAppRefreshTask:
                manager.handleAppRefresh(task: refreshTask)
            default:
                task.setTaskCompleted(success: false)
            }
        }
    }
}

import SwiftUI
import HealthKit

/// 用于心率监测的 watchOS 应用程序
@main
struct HeartMonitorApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        WKNotificationScene(
            controller: NotificationController.self,
            category: "heartAlert"
        )
    }
}

struct ContentView: View {
    @State private var heartRate: Double = 0
    private let healthStore = HKHealthStore()

    var body: some View {
        TabView {
            HeartRateView(rate: heartRate)
                .tabItem { Label("心率", systemImage: "heart.fill") }

            StepsView()
                .tabItem { Label("步数", systemImage: "figure.walk") }

            SettingsView()
                .tabItem { Label("设置", systemImage: "gear") }
        }
        .tabViewStyle(.page)
        .onAppear(perform: setupHealthKit)
    }

    private func setupHealthKit() {
        guard HKHealthStore.isHealthDataAvailable() else { return }
        let heartType = HKQuantityType(.heartRate)

        healthStore.requestAuthorization(toShare: nil, read: [heartType]) { success, error in
            guard success else { return }
            startHeartRateQuery()
        }
    }

    private func startHeartRateQuery() {
        let heartType = HKQuantityType(.heartRate)
        let query = HKObserverQuery(sampleType: heartType, predicate: nil) { _, _, error in
            guard error == nil else { return }
            fetchLatestHeartRate()
        }
        healthStore.execute(query)
    }

    private func fetchLatestHeartRate() {
        let heartType = HKQuantityType(.heartRate)
        let sort = NSSortDescriptor(key: HKSampleSortIdentifierStartDate, ascending: false)
        let query = HKSampleQuery(sampleType: heartType, predicate: nil,
                                    limit: 1, sortDescriptors: [sort]) { _, samples, _ in
            guard let sample = samples?.first as? HKQuantitySample else { return }
            let rate = sample.quantity.doubleValue(for: HKUnit(from: "count/min"))
            DispatchQueue.main.async { heartRate = rate }
        }
        healthStore.execute(query)
    }
}

struct HeartRateView: View {
    let rate: Double

    var body: some View {
        VStack(spacing: 12) {
            Image(systemName: "heart.fill")
                .foregroundStyle(.red)
                .font(.system(size: 48))
                .symbolEffect(.pulse)

            Text("\(Int(rate))")
                .font(.system(.title, design: .rounded))
                .contentTransition(.numericText())
                .bold()

            Text("次/分")
                .font(.caption)
                .foregroundStyle(.secondary)
        }
    }
}

import WatchConnectivity

/// iPhone 和 Apple Watch 之间的同步管理器
final class ConnectivityManager: NSObject, WCSessionDelegate {

    static let shared = ConnectivityManager()
    private let session = WCSession.default

    override private init() {
        super.init()
        session.delegate = self
        session.activate()
    }

    // MARK: — 从 iPhone 向手表发送数据
    func sendWorkoutData(_ data: [String: Any]) {
        guard session.isReachable else {
            // 如果手表不可用 — 保存在上下文中
            try? session.updateApplicationContext(data)
            return
        }
        session.sendMessage(data, replyHandler: nil) { error in
            print("Send error: \(error.localizedDescription)")
        }
    }

    // MARK: — 在手表上接收数据
    func session(_ session: WCSession,
                 didReceiveMessage message: [String: Any]) {
        DispatchQueue.main.async {
            NotificationCenter.default.post(
                name: NSNotification.Name("dataReceived"),
                object: message
            )
        }
    }

    func session(_ session: WCSession,
                 activationDidCompleteWith activationState: WCSessionActivationState,
                 error: Error?) {
        print("WCSession activated: \(activationState.rawValue)")
    }

    // 在 watchOS 上不需要，但对协议是强制性的
    func sessionDidBecomeInactive(_ session: WCSession) {}
    func sessionDidDeactivate(_ session: WCSession) {
        session.activate()
    }
}