Swift HealthKit HKStatisticsCollectionQuery statisticsUpdateHandler并不总是被调用

Question

我有一个测试项目，在这个测试项目中，我得到了一个用户在一周内每天下降的总次数。initialResultsHandler每一次都能完美地工作，但是statisticsUpdateHandler并不总是启动。如果您启动应用程序，然后转到健康应用程序并手动插入falls，切换回测试应用程序，您将看到今天更新的总数。在现实中，这是工作的前3-6次。从那以后，statisticsUpdateHandler就不再被打电话了。

奇怪的是，如果您删除数据，然后返回到测试应用程序，或者从比现在更早的时间添加数据，那么statisticsUpdateHandler就会被调用。这使我认为这与statisticsUpdateHandler结束日期有关。

苹果文档是相当清楚的，但是我担心他们可能遗漏了一些东西。

如果此属性设置为零，统计信息收集查询将在计算完初始结果后立即自动停止。如果此属性不是零，则查询的行为与观察者查询类似。它继续运行，监视HealthKit存储。如果将任何新的、匹配的示例保存到存储区，或者从存储中删除任何现有的匹配示例，则查询将在后台队列上执行更新处理程序。

是否有任何理由不调用statisticsUpdateHandler？我在下面包括了一个测试项目。

struct Falls: Identifiable{
    let id = UUID()
    let date: Date
    let value: Int
    
    var formattedDate: String{
        let formatter = DateFormatter()
        formatter.setLocalizedDateFormatFromTemplate("MM/dd/yyyy")
        return formatter.string(from: date)
    }
}

struct ContentView: View {
    @StateObject var manager = HealthKitManager()
    
    var body: some View {
        NavigationView{
            List{
                Text("Updates: \(manager.updates)")
                ForEach(manager.falls){ falls in
                    HStack{
                        Text(falls.value.description)
                        Text(falls.formattedDate)
                    }
                }
            }
            .overlay(
                ProgressView()
                    .scaleEffect(1.5)
                    .opacity(manager.isLoading ? 1 : 0)
            )
            .navigationTitle("Falls")
        }
    }
}

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

class HealthKitManager: ObservableObject{
    let healthStore = HKHealthStore()
    let fallType   = HKQuantityType.quantityType(forIdentifier: .numberOfTimesFallen)!
    @Published var isLoading = false
    @Published var falls = [Falls]()
    @Published var updates = 0

    init() {
        let healthKitTypesToRead: Set<HKSampleType> = [fallType]

        healthStore.requestAuthorization(toShare: nil, read: healthKitTypesToRead) { (success, error) in
            if let error = error{
                print("Error: \(error)")
            } else if success{
                self.startQuery()
            }
        }
    }
    
    func startQuery(){
        let now = Date()
        let cal = Calendar.current
        let sevenDaysAgo = cal.date(byAdding: .day, value: -7, to: now)!
        let startDate = cal.startOfDay(for: sevenDaysAgo)
        let predicate = HKQuery.predicateForSamples(withStart: startDate, end: now, options: [.strictStartDate, .strictEndDate])
        
        var interval = DateComponents()
        interval.day = 1
        
        // start from midnight
        let anchorDate = cal.startOfDay(for: now)
       
        let query = HKStatisticsCollectionQuery(
            quantityType: fallType,
            quantitySamplePredicate: predicate,
            options: .cumulativeSum,
            anchorDate: anchorDate,
            intervalComponents: interval
        )
        
        query.initialResultsHandler = { query, collection, error in
            guard let collection = collection else {
                print("No collection")
                DispatchQueue.main.async{
                    self.isLoading = false
                }
                return
            }
            
            collection.enumerateStatistics(from: startDate, to: Date()){ (result, stop) in
                guard let sumQuantity = result.sumQuantity() else {
                    return
                }
                
                let totalFallsForADay = Int(sumQuantity.doubleValue(for: .count()))
                let falls = Falls(date: result.startDate, value: totalFallsForADay)
                print(falls.value, falls.formattedDate)
                
                DispatchQueue.main.async{
                    self.falls.insert(falls, at: 0)
                }
            }
            
            print("initialResultsHandler done")
            DispatchQueue.main.async{
                self.isLoading = false
            }
        }
        
        
        query.statisticsUpdateHandler = { query, statistics, collection, error in
            print("In statisticsUpdateHandler...")
            guard let collection = collection else {
                print("No collection")
                DispatchQueue.main.async{
                    self.isLoading = false
                }
                return
            }
            
            DispatchQueue.main.async{
                self.isLoading = true
                self.updates += 1
                self.falls.removeAll(keepingCapacity: true)
            }
            
            collection.enumerateStatistics(from: startDate, to: Date()){ (result, stop) in
                guard let sumQuantity = result.sumQuantity() else {
                    return
                }
                
                let totalFallsForADay = Int(sumQuantity.doubleValue(for: .count()))
                let falls = Falls(date: result.startDate, value: totalFallsForADay)
                print(falls.value, falls.formattedDate)
                print("\n\n")

                DispatchQueue.main.async{
                    self.falls.insert(falls, at: 0)
                }
            }
            
            print("statisticsUpdateHandler done")
            DispatchQueue.main.async{
                self.isLoading = false
            }
        }
        
        
        isLoading = true
        healthStore.execute(query)
    }
}

Answer 1

我非常专注于statisticsUpdateHandler以及开始和结束时间，所以我没有注意查询本身。事实证明，谓词就是问题所在。通过给它一个结束日期，它永远不会在初始谓词结束日期之外寻找样本。

将谓词改为该谓词解决了这个问题：

let predicate = HKQuery.predicateForSamples(withStart: startDate, end: nil, options: [.strictStartDate])