上一篇我们介绍了如果创建Apple Watch项目，以及简单的显示UI、创建交互。这一篇我们将通过HealthKit实现在Apple Watch上实时显示用户的心率情况。

1、创建项目

同上一篇一样，我们只创建适用于Watch的App项目，项目名称为MyHeartRate

创建项目

2、创建工具类HeartRateManager

创建新的Swift文件，名称为HeartRateManager，用于请求权限、获取心率数据。完整代码如下：

import UIKit
import HealthKit

class HeartRateManager: NSObject,ObservableObject,HKWorkoutSessionDelegate,HKLiveWorkoutBuilderDelegate {
    @Published var state:Bool = false
    @Published var heartRate: Double = 0
    private var session:HKWorkoutSession!
    private var builder: HKLiveWorkoutBuilder!
    private let healthStore = HKHealthStore()
    
    /// 公开方法：请求权限
    func getAuthorization() {
        let typesToShare: Set = [
            HKQuantityType.workoutType()
        ]
        
        // 心率
        let heartRate =  HKQuantityType.quantityType(forIdentifier: .heartRate)
        let typesToRead:Set = [heartRate!]
        
        // 请求所需权限
        healthStore.requestAuthorization(toShare: typesToShare, read: typesToRead) { (succ, error) in
            if !succ {
                fatalError("Error requesting authorization from health store: \(String(describing: error)))")
            }
        }
    }
    
    /// 公开方法：开始健身
    func startWorkout() {
        /// 健身类型
        let configuration = HKWorkoutConfiguration()
        configuration.activityType = .mindAndBody
        configuration.locationType = .indoor
        
        do {
            session = try HKWorkoutSession(healthStore: healthStore, configuration: configuration)
            builder = session.associatedWorkoutBuilder()
        } catch {
            fatalError("Unable to create the workout session!")
        }
        
        // 设置session and builder.
        session.delegate = self
        builder.delegate = self
        
        /// 设置 builder的数据源
        builder.dataSource = HKLiveWorkoutDataSource(healthStore: healthStore, workoutConfiguration: configuration)
        // 开始健身session和开始监听数据
        session.startActivity(with: Date())
        builder.beginCollection(withStart: Date()) { (succ, error) in
            if !succ {
                fatalError("Error beginning collection from builder: \(String(describing: error)))")
            }
        }
        DispatchQueue.main.async { [weak self] in
            self?.state = true
        }
    }
    
    // 公开方法：停止健身session
    func stopWorkout() {
        session.end()
        builder.endCollection(withEnd: Date()) { (success, error) in
            self.builder.finishWorkout { (workout, error) in
                DispatchQueue.main.async() {
                    self.session = nil
                    self.builder = nil
                }
            }
        }
        DispatchQueue.main.async { [weak self] in
            self?.state = false
        }
    }
    
    /// 数据更新回调
    func workoutBuilder(_ workoutBuilder: HKLiveWorkoutBuilder, didCollectDataOf collectedTypes: Set<HKSampleType>) {
        for type in collectedTypes {
            if let quantityType = type as? HKQuantityType {
                switch quantityType {
                case HKQuantityType.quantityType(forIdentifier: .heartRate):
                    let statistics = workoutBuilder.statistics(for: quantityType)
                    let heartRateUnit = HKUnit.count().unitDivided(by: HKUnit.minute())
                    let value = statistics!.mostRecentQuantity()?.doubleValue(for: heartRateUnit)
                    let stringValue = String(Int(Double(round(1 * value!) / 1)))
                    DispatchQueue.main.async {
                        self.heartRate = Double(round(1 * value!) / 1)
                    }
                default:
                    return
                }
            }
        }
    }
    
    func workoutBuilderDidCollectEvent(_ workoutBuilder: HKLiveWorkoutBuilder) {
        // Retreive the workout event.
        guard let workoutEventType = workoutBuilder.workoutEvents.last?.type else { return }
        print("[workoutBuilderDidCollectEvent] Workout Builder changed event: \(workoutEventType.rawValue)")
    }
    
    func workoutSession(_ workoutSession: HKWorkoutSession, didChangeTo toState: HKWorkoutSessionState, from fromState: HKWorkoutSessionState, date: Date) {
        print("[workoutSession] Changed State: \(toState.rawValue)")
    }
    
    func workoutSession(_ workoutSession: HKWorkoutSession, didFailWithError error: Error) {
        print("[workoutSession] Encountered an error: \(error)")
    }
    
}

定义getAuthorization、startWorkout和stopWorkout三个方法，供后面的UI调用。而最底部的4个方法分别是HKWorkoutSessionDelegate,HKLiveWorkoutBuilderDelegate协议要求实现的。

3、创建UI

回到ContentView，利用上一步的HeartRateManager提供的数据和方法更新页面数据以及实现交互，完整代码如下：

import SwiftUI

struct ContentView: View {
    @StateObject private var heartRateManager = HeartRateManager()
    
    var body: some View {
        if heartRateManager.state {
            VStack {
                Text("心率:\(Int(heartRateManager.heartRate))")
                    .font(.title2)
                Button(action: {
                    heartRateManager.stopWorkout()
                }) {
                    Text("结束")
                        .font(.headline)
                }
            }
        }else {
            VStack {
                Button(action: {
                    heartRateManager.startWorkout()
                }) {
                    Text("开始")
                        .font(.headline)
                }
            }.onAppear() {
                heartRateManager.getAuthorization()
            }
        }
    }
}

4、添加权限

在Targets-MyHeartRateWatch-Sigining&Capabilities中添加HealthKit：

Capability

在info.plist文件中，添加对应读写健康数据权限的描述：

权限

5、运行查看效果

运行后，点击开始按钮，即可实时查看心率：

效果

完整代码下载

下一篇，将实现将心率数据实时传输给iOS APP