如何检查HealthKit功能何时完成(Swift)

Question

好吧,标题真的说明了一切,我无法在任何适合我的地方找到答案,所以我转向StackOverFlow.我正在尝试获取用户步数并将该值分配给UILabel.所以这里是我的一些代码(请注意,此函数包含在另一个类中,因此标签不在此函数的范围内):

func readTodayHealthData() -> Int {
        var stepCount: Int = 0
        func getStepsHealthData() {
        let stepsUnit = HKUnit.countUnit()
        let sumOption = HKStatisticsOptions.CumulativeSum
        let stepsHealthDataQuery = HKStatisticsQuery(quantityType: stepsHealth, quantitySamplePredicate: predicate, options: sumOption) {
            query, results, error in
            if let sumQuantity = results?.sumQuantity() {
                dispatch_async(dispatch_get_main_queue(), {
                    stepCount = sumQuantity.doubleValueForUnit(stepsUnit) * 2
                })
            }
        }
        healthKitStore?.executeQuery(stepsHealthDataQuery)
    }
  return stepCount
}
//Set UILabel Value
//**This code is in my View Controller which is in a separate class as a result this label is NOT within the scope of this function.**
myLabel.text = String(readTodayHealthData)

然后,当我在实际设备上运行应用程序时,我看到标签文本为零,我知道我今天已经做了一些行走:).所以,我认为问题在于,当我尝试设置标签值时,函数尚未完全执行.

我知道这一点,因为当我使用延迟功能并等待两秒钟时,我最终得到一个值,但如果我不等待,那么我得到零值.

所以,主要的问题是:如何检查,当功能被完全执行完毕？

Answer 1

问题是你正在使用的操作是异步的,那么你需要正确处理,你有两个选择:

1. 更新UILabel在completionHandler自己的函数中getStepsHealthData在主线程,因为你要更新UI,就像这样:

   func getStepsHealthData() {
        var stepCount: Int = 0
        let stepsUnit = HKUnit.countUnit()
        let sumOption = HKStatisticsOptions.CumulativeSum
   
        let stepsHealthDataQuery = HKStatisticsQuery(quantityType: stepsHealth, quantitySamplePredicate: predicate, options: sumOption) {
           query, results, error in
             if let sumQuantity = results?.sumQuantity() {
                dispatch_async(dispatch_get_main_queue(), {
                  stepCount = sumQuantity.doubleValueForUnit(stepsUnit) * 2
   
                  //Set UILabel Value
                  myLabel.text = String(stepCount)
                })
             }
        }
        healthKitStore?.executeQuery(stepsHealthDataQuery)
   }
   

   而且你不需要返回任何东西.

2. 如果要从函数返回步数,则需要使用闭包进行一些操作并修改函数,如下所示:

   func getStepsHealthData(completion: (steps: Int) -> ()) {
        var stepCount: Int = 0
        let stepsUnit = HKUnit.countUnit()
        let sumOption = HKStatisticsOptions.CumulativeSum
   
        let stepsHealthDataQuery = HKStatisticsQuery(quantityType: stepsHealth, quantitySamplePredicate: predicate, options: sumOption) {
           query, results, error in
             if let sumQuantity = results?.sumQuantity() {
                 stepCount = sumQuantity.doubleValueForUnit(stepsUnit) * 2
                 completion(stepCount)
             }
        }
        healthKitStore?.executeQuery(stepsHealthDataQuery)
   }
   

   然后你可以从外面这样称呼它:

   self.getStepsHealthData() { (steps) -> Void in
      dispatch_async(dispatch_get_main_queue(), {
          //Set UILabel Value
          myLabel.text = String(stepCount)
      })
   }
   

我希望这对你有帮助.