Fast gyro rotation, step, roll

Question

Fast gyro rotation, step, roll

I am doing a project for my school, for the subject of programming. I am working in Xcode in Swift. I would like to make an application that uses a gyroscope. I don't know, but somehow it won't work on my iphone due to some errors in Xcode that I don't know how to fix. When I run the program, it says "fatal error: unexpectedly found nil when unwrapping optional value (Lldb)" The main thing in my project is to display rotations (yaw, step, roll) in degrees on the iphone screen using a gyroscope. I would be very grateful if someone could help me with this. Thank you in advance.

Code in my ViewController:

import UIKit
import CoreMotion

class ViewController: UIViewController {

    var currentMaxRotX: Double = 0.0
    var currentMaxRotY: Double = 0.0
    var currentMaxRotZ: Double = 0.0

    let motionManager = CMMotionManager()

    @IBOutlet var rotX : UILabel! = nil
    @IBOutlet var rotY : UILabel! = nil
    @IBOutlet var rotZ : UILabel! = nil

    @IBOutlet var maxRotX : UILabel! = nil
    @IBOutlet var maxRotY : UILabel! = nil
    @IBOutlet var maxRotZ : UILabel! = nil


    @IBOutlet weak var RollLabel: UILabel! = nil

    @IBOutlet weak var PitchLabel: UILabel! = nil

    @IBOutlet weak var YawLabel: UILabel! = nil

    override func viewDidLoad() {

        if motionManager.gyroAvailable {

            if !motionManager.gyroActive {
                motionManager.gyroUpdateInterval = 0.2
                motionManager.startGyroUpdates()
                //motionManager = [[CMMotionManager alloc]init]; should I use this ???
                //motionManager.deviceMotionUpdateInterval = 0.2;
                //motionManager.startDeviceMotionUpdates()

                 motionManager.startGyroUpdatesToQueue(NSOperationQueue.currentQueue(), withHandler: {(gyroData: CMGyroData!, error: NSError!)in
                     self.outputRotationData(gyroData.rotationRate)
                     if (error != nil)
                     {
                         println("\(error)")
                     }
                 })      
            }
       } else {
              var alert = UIAlertController(title: "No gyro", message: "Get a Gyro", preferredStyle: UIAlertControllerStyle.Alert)
              alert.addAction(UIAlertAction(title: "Click", style: UIAlertActionStyle.Default, handler: nil))
              self.presentViewController(alert, animated: true, completion: nil)
    }


     super.viewDidLoad()
    }

    // radians to degrees
    func radians(fromDegrees degrees: Double) -> Double {
        return 180 * degrees / M_PI
    }

    func outputRotationData(rotation:CMRotationRate)
    {
        rotX.text = NSString(format:"Rotation X: %.4f",rotation.x)
        if fabs(rotation.x) > fabs(currentMaxRotX)
        {
            currentMaxRotX = rotation.x
        }

        rotY.text = NSString(format:"Rotation Y: %.4f", rotation.y)
        if fabs(rotation.y) > fabs(currentMaxRotY)
        {
            currentMaxRotY = rotation.y
        }
        rotZ.text = NSString(format:"Rotation Z:%.4f", rotation.z)
        if fabs(rotation.z) > fabs(currentMaxRotZ)
        {
            currentMaxRotZ = rotation.z
        }

        maxRotX.text = NSString(format:"Max rotation X: %.4f", currentMaxRotX)
        maxRotY.text = NSString(format:"Max rotation Y:%.4f", currentMaxRotY)
        maxRotZ.text = NSString(format:"Max rotation Z:%.4f", currentMaxRotZ)

        var attitude = CMAttitude()
        var motion = CMDeviceMotion()
        motion = motionManager.deviceMotion
        attitude = motion.attitude


        YawLabel.text = NSString (format: "Yaw: %.2f", attitude.yaw)    //radians to degress NOT WORKING
        PitchLabel.text = NSString (format: "Pitch: %.2f", attitude.pitch)//radians to degress NOT WORKING
        RollLabel.text = NSString (format: "Roll: %.2f", attitude.roll)//radians to degress NOT WORKING
      }

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

+3

ios iphone xcode swift core-motion

Moonwalker4z 05 jan. 15 at 16:24

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1 answer

Nate cook · Accepted Answer · 2015-01-05T18:06:25+0000

In these two lines, you are working with implicitly expanded options: you use them without ?

or !

, but they will break your program if they are nil

. In this case, it motionManager.deviceMotion

is nil

because you have not called motionManager.startDeviceMotionUpdates()

access before.

Your method viewDidLoad

is the right place for this:

override func viewDidLoad() {

    if motionManager.gyroAvailable {
        motionManager.deviceMotionUpdateInterval = 0.2;
        motionManager.startDeviceMotionUpdates()

        motionManager.gyroUpdateInterval = 0.2
        motionManager.startGyroUpdatesToQueue(NSOperationQueue.currentQueue()) {
           [weak self] (gyroData: CMGyroData!, error: NSError!) in

           self?.outputRotationData(gyroData.rotationRate)
           if error != nil {
               println("\(error)")
           }
        }
    } else {
        // alert message
    }

    super.viewDidLoad()
}

There are a few additional changes there:

You don't need to call startGyroUpdates()

before startGyroUpdatesToQueue()

.
Swift uses trailing closure for completion handlers like this one, which are more readable and writeable.
To avoid the reference loop, declare self

as weak

inside the completion handler -. This then requires when using an additional chain when accessingself

Fast gyro rotation, step, roll

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