在我们的应用程序中,我们查询 HealthKit 以获取过去 7 天的步数,每天汇总,以午夜为基准。所以范围是 D-6 午夜到明天午夜(因为我们想要今天的步骤到现在为止)。
它有效,我们总是能够获取过去 6 天的数据,除了今天的数据始终为 0。
但奇怪的是,如果我们随后打开 iOS 8.0 附带的默认 iHealth 应用程序,它会计算健康数据并在图表中显示今天的步骤。然后,如果我们重新打开应用程序并重新加载图表数据,今天的步骤就会奇迹般地出现,与“iHealth”显示的内容相符。
那么 iPhone 是否会仅在午夜自动生成每日步数,并将其缓存起来还是其他什么?我们是否需要单独调用才能计算today's在检索任何健康指标之前的数据或其他内容?
这是我们调用来获取数据的函数:
func queryDailyStats(metric: NSString!, handler: ([NSDate: Int] -> Void)!) {
let quantityType = HKObjectType.quantityTypeForIdentifier(metric)
let calendar = NSCalendar.currentCalendar()
let now = NSDate()
let preservedComponents: NSCalendarUnit = (.CalendarUnitYear | .CalendarUnitMonth | .CalendarUnitDay)
let midnight: NSDate! = calendar.dateFromComponents(calendar.components(preservedComponents, fromDate:now))
let dailyInterval = NSDateComponents()
dailyInterval.day = 1
let tomorrow = calendar.dateByAddingUnit(.MonthCalendarUnit, value: 1, toDate: midnight, options: nil)
let oneMonthAgo = calendar.dateByAddingUnit(.MonthCalendarUnit, value: -1, toDate: midnight, options: nil)
let oneWeekAgo = calendar.dateByAddingUnit(.DayCalendarUnit, value: -6, toDate: midnight, options: nil) // only need to start from 6 days back
// need tomorrow's midnight as end date to get all of today's data
let predicate = HKQuery.predicateForSamplesWithStartDate(oneWeekAgo, endDate: tomorrow, options: .None)
let query = HKStatisticsCollectionQuery(
quantityType: quantityType,
quantitySamplePredicate: predicate,
options: .CumulativeSum,
anchorDate: midnight,
intervalComponents: dailyInterval
)
query.initialResultsHandler = { query, results, error -> Void in
var data:[NSDate: Int] = [:]
if error != nil {
println(error)
} else {
results.enumerateStatisticsFromDate(oneWeekAgo, toDate: midnight) { statistics, stop in
if let quantity = statistics.sumQuantity() {
let date = statistics.startDate
let value = Int(quantity.doubleValueForUnit(HKUnit.countUnit()))
data[date] = value
}
}
}
handler(data)
}
self.healthKitStore.executeQuery(query)
}