CoreMotion主线程检查器警告，仅出现在2018型号iPhone上

Question

The following is an extremely simplified version of the issue:

import UIKit
import CoreMotion

class ViewController: UIViewController {
    private let manager = CMMotionManager()
    private let interval = 0.01

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        startUpdates()
    }

    private func startUpdates() {
        let queue = OperationQueue()
        queue.name = "com.demo.motion"
        queue.qualityOfService = .userInteractive
        queue.maxConcurrentOperationCount = 1
        manager.accelerometerUpdateInterval = interval
        manager.startAccelerometerUpdates(to: queue) { _, _ in }
    }
}

When I run this on an iPhone XR, I will receive the following:

Main Thread Checker: UI API called on a background thread: -[UIApplication applicationState] PID: 1237, TID: 147763, Thread name: com.apple.CoreMotion.MotionThread, Queue name: com.apple.root.default-qos.overcommit, QoS: 0

• My device is running 12.3 , which is currently the latest iOS release
• Running this on various iPads (pre 2018), iPhone 8, iPhone 6S, and other older models, the issue does not appear.
• Changing the qualityOfService has no impact on this (my preference is to use utility )
• Out of curiosity, I wrapped the entire startUpdates() function around a main dispatch with no success

Based on the queue name and when this is occurring, my assumption is that this is something internal that is just getting exposed by the faster processor in the XR, versus the older devices.

Answer 1

This is a known issue that has been reported to Apple with a radar linked here .

Hopefully, it will be addressed soon but I did not see any entries for it on SO and wanted to have something available for others coming across it.

If you can, please file a dupe.

Fortunately, I have not seen any adverse impacts of this yet .