Question

我正在尝试显示CMPedometer的节奏和速度数据。当我连接手机运行应用程序时，它会立即通过print("...")功能将数据输出写入控制台，但需要多次转动，直到它显示UILabel中的数据。如何尽可能快地获取数据，以便我可以使用它们？

最好，扎克

import UIKit
import CoreMotion

class ViewController: UIViewController {
    let pedometer = CMPedometer()
    @IBOutlet weak var paceLabel: UILabel!
    @IBOutlet weak var cadenceLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        guard CMPedometer.isCadenceAvailable() && CMPedometer.isPaceAvailable() else{
            print("Pace and cadence data are not available")
            return
        }         
        let oneWeekAgo = NSDate(timeIntervalSinceNow: -(7 * 24 * 60 * 60))
        pedometer.startUpdates(from: oneWeekAgo as Date) {data, error in
            guard let pData = data , error == nil else{
                return
            }
            //The current pace of the user, measured in seconds per meter. (1 step = 83cm?)
            if let pace = pData.currentPace{
                print("Pace = \(pace)")
                self.paceLabel.text = "Pace = \(round(Double(pace))*10/10)"
            }
            //The rate at which steps are taken, measured in steps per second.
            if let cadence = pData.currentCadence{
                self.cadenceLabel.text = "Cadence = \(cadence))"
                print("Cadence = \(cadence)")
            }
        }// -----------------oneWeekAgo        
    }// -----------------ViewDidLoad

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}//-------------------- UIViewController

Answer 1

在后台线程上调用更新块，您需要在主线程上更新UI。将调度中的UI更新调用包装回主线程：

Dispatch.main.async {
    //The current pace of the user, measured in seconds per meter. (1 step = 83cm?)
    if let pace = pData.currentPace{
        print("Pace = \(pace)")
        self.paceLabel.text = "Pace = \(round(Double(pace))*10/10)"
    }

    //The rate at which steps are taken, measured in steps per second.
    if let cadence = pData.currentCadence{
        self.cadenceLabel.text = "Cadence = \(cadence))"
            print("Cadence = \(cadence)")
        }
    }
}

为什么“打印到控制台”比“.text into label”

1 个答案: