Swift gyroscope yaw, pitch, roll
Solution 1
In these two lines you're working with implicitly unwrapped optionals: you use them without ?
or !
, but they'll crash your program if they're nil
. In this case, motionManager.deviceMotion
is nil
because you haven't called motionManager.startDeviceMotionUpdates()
prior to that access.
Your viewDidLoad
method is the right place to do 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()
beforestartGyroUpdatesToQueue()
. - Swift uses trailing closures for completion handlers like this one - nicer to write and read.
- To avoid a reference cycle, declare
self
asweak
inside a completion handler - this then requires using optional chaining when accessingself
.
Solution 2
"guard", "if let", and optional chaining are the key to safely unwrap optionals, here is a Swift4 answer:
let motionManager = CMMotionManager()
override func viewDidLoad() {
if motionManager.isGyroAvailable {
motionManager.deviceMotionUpdateInterval = 0.2;
motionManager.startDeviceMotionUpdates()
motionManager.gyroUpdateInterval = 0.2
guard let currentQueue = OperationQueue.current else { return }
motionManager.startGyroUpdates(to: currentQueue) { (gyroData, error) in
// Do Something, call function, etc
if let rotation = gyroData?.rotationRate {
print(rotation)
print(rotation.x)
print(rotation.y)
print(rotation.z)
}
if error != nil {
print("\(error)")
}
}
}
}
Moonwalker4z
Updated on June 24, 2022Comments
-
Moonwalker4z almost 2 years
I'm doing a project for my school, for a programming subject. I'm working in Xcode in Swift. I would like to make an application that uses Gyroscope. I don't know but somehow it won't run on my iphone because of some errors in Xcode that I don't know how to fix.When I run the program is says "fatal error: unexpectedly found nil while unwrapping an Optional value (lldb)" The main thing of my project is to display rotations (yaw,pitch,roll) in degrees on iphone screen using gyroscope. I would be really grateful if someone help me with this. Thank you in advance.
The 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. } }