Naitian Naitian - 5 months ago 21
iOS Question

Motion Manager is not working in Swift

I am try to use motion manager in Swift but the log inside my update block never prints.

var motionManager: CMMotionManager = CMMotionManager()
motionManager.accelerometerUpdateInterval = 0.01
println(motionManager.deviceMotionAvailable) // print true
println(motionManager.deviceMotionActive) // print false
motionManager.startDeviceMotionUpdatesToQueue(NSOperationQueue.currentQueue(), withHandler:{
deviceManager, error in
println("Test") // no print
})

println(motionManager.deviceMotionActive) // print false


My Objective-C implementation works fine. Does anyone know why my update block isn't being called?

Answer

That's because the motion manager instance is being thrown out when the method returns. You should make a property on your class to contain the motion manager. Additionally, it looks like you were only changing the manger's accelerometerUpdateInterval and then monitoring device motion changes. You should set the deviceMotionUpdateInterval property instead.

import CoreMotion

class ViewController: UIViewController {
    let motionManager: CMMotionManager = CMMotionManager()

    override func viewDidLoad() {
        super.viewDidLoad()

        motionManager.deviceMotionUpdateInterval = 0.01
        motionManager.startDeviceMotionUpdatesToQueue(NSOperationQueue.currentQueue(), withHandler:{
            deviceManager, error in
            println("Test") // no print
        })

        println(motionManager.deviceMotionActive) // print false
    }
}