isBatteryMonitoringEnabled属性状态未转为true

Question

我正在尝试制作一个简单的电池级打印应用程序，但我无法将isBatteryMonitoringEnabled属性状态变为true 。 我已经完成了所有事情，但我没有这样做。

所以这就是我到目前为止所做的：

import UIKit

class ViewController: UIViewController {

    @IBAction func Start(_ sender: Any) {
        UIDevice.current.isBatteryMonitoringEnabled = true

        var batteryLevel: Float {
            return UIDevice.current.batteryLevel
        }

        print(batteryLevel)       
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

每当我在模拟器上编译并运行此代码时，我总是得到-1.0作为输出（这意味着状态unknown ）

如果有人帮我解决我的问题，我将非常感激！

Answer 1

在实际设备上运行时，以下内容适用于我。 在应用程序委托中，我启用了电池监控：

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    UIDevice.current.isBatteryMonitoringEnabled = true
    return true
}

我有View Controller，我可以在设备插入或拔出时手动检查设备是否正在充电或接收通知。

class ViewController：UIViewController {@IBOutlet weak var chargingLabel：UILabel！

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(batteryStateChanged(_:)), name: UIDevice.batteryStateDidChangeNotification, object: nil)
    updateBatteryUI()
}

@objc func batteryStateChanged(_ notification:Notification) {
    if UIDevice.current.batteryState == .charging {
        UIApplication.shared.isIdleTimerDisabled = true
        chargingLabel.text = "Charging"
    } else {
        chargingLabel.text = "Not Charging"
    }
}

func updateBatteryUI() {
    if UIDevice.current.batteryState == .charging {
        UIApplication.shared.isIdleTimerDisabled = true
        chargingLabel.text = "Charging"
    } else {
        chargingLabel.text = "Not Charging"
    }
}

}