How to detect orientation change?

Question

I am using Swift and I want to be able to load a UIViewController when I rotate to landscape, can anyone point me in the right direction?

I Can't find anything online and a little bit confused by the documentation.

Answer 1

Swift 3 | UIDeviceOrientationDidChange Notification Observed Too Often

The following code prints "deviceDidRotate" every time your device changes orientation in 3D space - regardless of a change from portrait to landscape orientation. For example, if you hold your phone in portrait orientation and tilt it forward and backward - deviceDidRotate() is called repeatedly.

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(
        self, 
        selector:  #selector(deviceDidRotate), 
        name: .UIDeviceOrientationDidChange, 
        object: nil
    )
}

func deviceDidRotate() {
    print("deviceDidRotate")
}

To work around this you could hold the previous device orientation and check for a change in deviceDidRotate().

var previousDeviceOrientation: UIDeviceOrientation = UIDevice.current.orientation

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(
        self, 
        selector:  #selector(deviceDidRotate), 
        name: .UIDeviceOrientationDidChange, 
        object: nil
    )
}

func deviceDidRotate() {
    if UIDevice.current.orientation == previousDeviceOrientation { return }
    previousDeviceOrientation = UIDevice.current.orientation
    print("deviceDidRotate")
}

Or you can use a different notification that only gets called when the device changes from landscape to portrait. In this case you'd want to use the UIApplicationDidChangeStatusBarOrientation notification.

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(
        self, 
        selector:  #selector(deviceDidRotate), 
        name: .UIApplicationDidChangeStatusBarOrientation, 
        object: nil
    )
}

func deviceDidRotate() {
    print("deviceDidRotate")
}

Answer 2

Use the new viewWillTransitionToSize(_:withTransitionCoordinator:)

Answer 3

Easy, this works in iOS8 and 9 / Swift 2 / Xcode7, just put this code inside your viewcontroller.swift. It will print the screen dimensions with every orientation change, you can put your own code instead:

override func didRotateFromInterfaceOrientation(fromInterfaceOrientation: UIInterfaceOrientation) {
        getScreenSize()
    }
    var screenWidth:CGFloat=0
    var screenHeight:CGFloat=0
    func getScreenSize(){
        screenWidth=UIScreen.mainScreen().bounds.width
        screenHeight=UIScreen.mainScreen().bounds.height
        print("SCREEN RESOLUTION: "+screenWidth.description+" x "+screenHeight.description)
    }

Answer 4

In Objective C

-(void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator

In swift

func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator)

Override this method to detect the orientation change.

Answer 5

Since iOS 8 this is the correct way to do it.

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    super.viewWillTransition(to: size, with: coordinator)

    coordinator.animate(alongsideTransition: { context in
        // This is called during the animation
    }, completion: { context in
        // This is called after the rotation is finished. Equal to deprecated `didRotate`
    })
}

Answer 6

I like checking the orientation notification because you can add this feature in any class, no needs to be a view or a view controller. Even in your app delegate.

    //ask the system to start notifying when interface change
    UIDevice.currentDevice().beginGeneratingDeviceOrientationNotifications()
    //add the observer
    NSNotificationCenter.defaultCenter().addObserver(
        self,
        selector: #selector(self.orientationChanged(_:)),
        name: UIDeviceOrientationDidChangeNotification,
        object: nil)

than caching the notification

    func orientationChanged(notification : NSNotification) {
        //your code there
    }