ios - 后台计时器非常慢

Question

我正在使用计时器，并尝试使其在后台运行。在模拟器上这工作正常，但在我的设备(iOS 11)上它非常慢:1 秒变成了 5 或 6 秒......

This is my code for run application in background:

backgroundTaskIdentifier = UIApplication.shared.beginBackgroundTask(
    expirationHandler:
      {UIApplication.shared.endBackgroundTask(self.backgroundTaskIdentifier!)}
    )

Info.plist: Application does not run in background : NO

我怎样才能让它发挥作用？

编辑:

这是我的计时器代码:

timer = Timer.scheduledTimer(timeInterval: 0.01, target: self, 
  selector:#selector(ViewController.updateTimer), userInfo: nil, repeats: true)

编辑2:

func updateTimer () {
    var j = 0
    for _ in rows {
        if (rows[j]["Playing"] as! Bool == true ) {
            rows[j]["time"] = (rows[j]["time"] as! Double + 0.01) as AnyObject
        // print(rows[j]["time"]) - PRINT OUTPUT HERE
            rows[j]["lastTime"] = (rows[j]["lastTime"] as! Double + 0.01) as AnyObject
        }
        if (rows[j]["lastTime"] as! Double > 60.0) {
            min[j] += 1
            rows[j]["lastTime"] = 0.00 as AnyObject
        }
        j += 1
    }
}

Answer 1

不要只打印可能从不同线程执行的输出，而是从主线程打印它。这就是您可能会看到延迟的原因:

DispatchQueue.main.async {
  print(rows[j]["time"])
}