UIDynamicAnimator - Move view based on Device Motion Roll - ios

Question

I am trying to read my devices Motion, specifically the Roll of the device when it is in Landscape Mode, and translate the angle returned into a Position of a UIView (Basically making a on screen "Level" to show the user that the phone is at an ideal angle).
This code gives the desired roll result, but for some reason is not updating the levelIndicator view as expected. I am not getting any errors, so I must be using UIPushBehavior incorrectly, but I am unclear what I need to fix. I am not sure about setting to new Y position of the indicator on Motion Update.
import UIKit
import AVFoundation
import CoreMotion
import GLKit
class CameraView: BaseViewController {
var animator : UIDynamicAnimator? = nil;
var currentRoll : Float = 0.0;
let manager = CMMotionManager()
let motionQueue = NSOperationQueue()
var countingDown:Bool = false;
#IBOutlet weak var levelIndicator: UIView!
#IBOutlet weak var level: UIView!
override func viewDidLoad() {
super.viewDidLoad()
self.animator = UIDynamicAnimator(referenceView: self.level)
let continuousPush: UIPushBehavior = UIPushBehavior(items: [levelIndicator], mode: UIPushBehaviorMode.Continuous)
self.animator?.addBehavior(continuousPush)
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(true)
self.startReadingMotion()
}
func startReadingMotion() {
if manager.deviceMotionAvailable {
manager.deviceMotionUpdateInterval = 0.1
manager.startDeviceMotionUpdatesToQueue(motionQueue, withHandler: checkStability)
}
}
func checkStability(motion: CMDeviceMotion!, error: NSError!) {
var orientation = UIDevice.currentDevice().orientation
if (error != nil) {
NSLog("\(error)")
}
var quat = motion.attitude.quaternion
//We Probably only need to check the Angle of the Roll (Phone Angle in Landscape mode)
var roll = GLKMathRadiansToDegrees(Float(atan2(2*(quat.y*quat.w - quat.x*quat.z), 1 - 2*quat.y*quat.y - 2*quat.z*quat.z))) ;
//Other Angles are available for more refinement to stabilty
//var pitch = GLKMathRadiansToDegrees(Float(atan2(2*(quat.x*quat.w + quat.y*quat.z), 1 - 2*quat.x*quat.x - 2*quat.z*quat.z)));
//var yaw = GLKMathRadiansToDegrees(Float(asin(2*quat.x*quat.y + 2*quat.w*quat.z)));
if(orientation == .LandscapeLeft) {
roll *= -1
}
if(roll > 100) {
roll = 100
} else if(roll < 0) {
roll = 0
}
self.currentRoll = roll
var pos = self.level.frame.height*CGFloat(roll/100)
var rect = self.levelIndicator.frame
rect.origin.y = pos
self.levelIndicator.frame = rect
if(roll > 85 && roll < 87) {
if(!countingDown) {
//This is the ideal roll position of the phone
self.levelIndicator.backgroundColor = UIColor.redColor()
}
} else {
countingDown = false;
self.levelIndicator.backgroundColor = UIColor.blackColor()
}
}
func stopReading() {
manager.stopDeviceMotionUpdates();
}
}

Answer 1

For anyone interested I ended up not using the UIDynamicAnimator for this but found a much simpler solution converting the returned Radians of the attitude change and using that to check the roll of the device. Also added a dispatch to the main queue to update the UI of the onscreen level.
func checkStability(motion: CMDeviceMotion!, error: NSError!) {
var orientation = UIDevice.currentDevice().orientation
if (error != nil) {
NSLog("\(error)")
}
var roll:Float = 0.0
if let attitude = motion.attitude {
roll = GLKMathRadiansToDegrees(Float(attitude.roll))
}
dispatch_async(dispatch_get_main_queue()) {
var pos = self.level.frame.height*CGFloat(roll/100)
var rect = self.levelIndicator.frame
rect.origin.y = self.level.frame.height-pos
self.levelIndicator.frame = rect
if(roll > 85 && roll < 90) {
//This is where I want the Roll to be
} else {
//The Roll is not correct yet
}
}
}