UIDevice.currentDevice（）。beginGeneratingDeviceOrientationNotifications（）无法正常工作

Question

I am trying to use the property UIDevice.currentDevice().orientation, so I have something like the following

UIDevice.currentDevice().beginGeneratingDeviceOrientationNotifications()
var orientation = UIDevice.currentDevice().orientation
switch orientation {
  case .Portrait:
    print("portrait")
    break
  case .PortraitUpsideDown: // Device oriented vertically, home button on the top
    print("upsidedown")
    magneticHeading += 180
    magneticHeading = magneticHeading % 360
    break
  case .LandscapeLeft: // Device oriented horizontally, home button on the right
    print("left")
    magneticHeading -= 90
    magneticHeading = magneticHeading % 360
    break
  case .LandscapeRight: // Device oriented horizontally, home button on the left
    print("right")
    magneticHeading += 90
    magneticHeading = magneticHeading % 360
    break
  case .FaceUp: // Device oriented flat, face up
    print("up")
    break
  case .FaceDown: // Device oriented flat, face down
    print("down")
    break
  case .Unknown:
    print("unknown")
    break
  default:
    print("default")
  }

I've look through lots of webpages and questions on Stack Overflow, all of them uses beginGeneratingDeviceOrientationNotifications() then it will work. However, my code won't work at all. In the switch statement, it always enter .Portrait no matter how I turn my phone. Does anyone know why?

Also, I actually want the device's orientation, instead of my viewcontroller's orientation. I need to know how is the device held, so I need to use currentDevice().orientation

I've also tried using the following:

var interfaceOrientation = UIApplication.sharedApplication().statusBarOrientation
switch interfaceOrientation {
  case .Unknown:
    print("1")
  case .Portrait:
    print("2")
  case .PortraitUpsideDown:
    print("3")
  case .LandscapeLeft:
    print("4")
  case .LandscapeRight:
    print("5")

again, no matter how I turn my phone, always enter .Portrait

Answer 1

Please check your xcode target general setting

Answer 2

After a long time of trying, I figured that it's because I locked the screen on the phone. It seems to be no way to check if the user has locked the phone.