iOS开发Swift获取设备电池级别始终返回-1.0求助

Hey there! Let's work through why you're getting -1.0 when trying to fetch the battery level. I've reviewed your code, and here are the key fixes and checks you need to make:

1. You're probably testing on the iOS Simulator #

The iOS Simulator doesn't have actual battery hardware, so it will always return -1.0 for batteryLevel no matter how you configure battery monitoring. This is the most common culprit here!

To get real battery data, you need to run your app on a physical iOS device (iPhone/iPad).

2. Add a notification listener for battery state changes #

While you've correctly enabled battery monitoring in viewDidLoad, the system might take a moment to fetch the initial battery data. Adding a notification listener ensures you get updates whenever the battery state (charging/discharging) changes, so you'll always have the latest level available.

Here's your updated code with this fix:

import UIKit

class FirstController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Enable battery monitoring
        UIDevice.current.isBatteryMonitoringEnabled = true
        // Listen for battery state changes to get updated level data
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(batteryStateChanged),
            name: UIDevice.batteryStateDidChangeNotification,
            object: nil
        )
    }
    
    deinit {
        // Clean up the notification observer to avoid memory leaks
        NotificationCenter.default.removeObserver(self)
    }
    
    var batteryLevel: Float {
        let rawLevel = UIDevice.current.batteryLevel
        // Return 0.0 instead of -1.0 if level is unavailable (for better UX)
        return rawLevel >= 0 ? rawLevel : 0.0
    }
    
    @objc private func batteryStateChanged() {
        // This will print the updated level whenever the battery state changes
        print("Updated Battery Level: \(batteryLevel)")
    }
    
    @IBAction func onButtonClick(_ sender: Any) {
        print("Battery monitoring enabled: \(UIDevice.current.isBatteryMonitoringEnabled)")
        print("Current Battery Level: \(batteryLevel)")
    }
}

Additional Notes #

• The -1.0 value from batteryLevel is Apple's official indicator that battery monitoring is disabled or the device can't provide battery data. Since you've enabled monitoring, this is almost certainly a simulator issue.
• On a physical device, you should see values between 0.0 (empty) and 1.0 (full) when you tap the button or when the battery state changes.

内容的提问来源于stack exchange，提问作者Sanjay Kumar