ios - 从 HealthStore 读取心率

Question

我正在尝试从 Healthkit 检索心率信息。

我的个人资料中有一些心率数据。

这是我的查询:

private func createStreamingQuery() -> HKQuery {
    let predicate = HKQuery.predicateForSamples(withStart: NSDate() as Date, end: nil, options: [])

    let query = HKAnchoredObjectQuery(type: heartRateType, predicate: predicate, anchor: nil, limit: Int(HKObjectQueryNoLimit)) {
        (query, samples, deletedObjects, anchor, error) -> Void in

        self.formatSamples(samples: samples)

    }

    query.updateHandler = { (query, samples, deletedObjects, anchor, error) -> Void in
        self.formatSamples(samples: samples)
    }

    return query
}

现在我的函数格式示例:

private func formatSamples(samples: [HKSample]?) {
    guard let heartRateSamples = samples as? [HKQuantitySample] else { return }

        guard let sample = heartRateSamples.first else{return}
        let value = sample.quantity.doubleValue(for: self.heartRateUnit)

        print("HeartRate: \(value)")
}

我已经调试过了，发现在“formatSamples”的第一行代码中，列表“samples”有很多值，

 guard let heartRateSamples = samples as? [HKQuantitySample] else { return } 

但是当我尝试获取此列表的第一个值时，突然我的列表为空并且它结束了该函数。这里->

guard let sample = heartRateSamples.first else{return}

我不明白为什么示例列表会自动从一行到下一行清空。

查询已执行。

@IBAction func readHeartRate(_ sender: Any) {
    self.healthStore.execute(self.createStreamingQuery())
}

你能帮我吗？

Answer 1

问题是我的谓词不正确。

这是我使用的正确谓词的示例。它将结果限制为最近 7 天。

let calendar = NSCalendar.current;
let now = NSDate();
let sevenDaysAgo = calendar.date(byAdding: .day, value: -7, to: now as Date);
let startDate = calendar.startOfDay(for: sevenDaysAgo!);

let predicate = HKQuery.predicateForSamples(withStart: startDate as Date, end: now as Date, options: [])