Detecting Device Rotation In Swift

OrientationMonitor.swift

import UIKit
import SwiftUI

@MainActor
@Observable
public final class OrientationMonitor {
    
    public enum RotationDirection: String {
        case anticlockwise
        case clockwise
        case unknown
    }
    
    public private(set) var current: UIDeviceOrientation
    public private(set) var lastRotation: RotationDirection
    
    public init() {
        current =  UIDevice.current.orientation
        lastRotation = .unknown
        
        Task {
            for await notification in NotificationCenter.default.notifications(named: UIDevice.orientationDidChangeNotification) {
                guard let device = notification.object as? UIDevice else { return }
                
                let newOrientation = device.orientation
                let direction = calculateRotationDirection(
                    newOrientation: newOrientation,
                    currentOrientation: current
                )
                
                current = newOrientation
                lastRotation = direction
            }
        }
    }
    
    private func calculateRotationDirection(
        newOrientation: UIDeviceOrientation,
        currentOrientation: UIDeviceOrientation
    ) -> RotationDirection {
        var direction: RotationDirection = .unknown
        
        switch newOrientation {
        case .unknown:
            return .unknown
        case .portrait:
            switch currentOrientation {
            case .portrait:
                direction = .unknown
            case .portraitUpsideDown:
                direction = .unknown
            case .landscapeLeft:
                direction = .clockwise
            case .landscapeRight:
                direction = .anticlockwise
            case .unknown, .faceUp, .faceDown:
                direction = .unknown
            @unknown default:
                direction = .unknown
            }
        case .portraitUpsideDown:
            switch currentOrientation {
            case .portrait:
                direction = .unknown
            case .portraitUpsideDown:
                direction = .unknown
            case .landscapeLeft:
                direction = .anticlockwise
            case .landscapeRight:
                direction = .clockwise
            case .unknown, .faceUp, .faceDown:
                direction = .unknown
            @unknown default:
                direction = .unknown
            }
        case .landscapeLeft:
            switch currentOrientation {
            case .portrait:
                direction = .anticlockwise
            case .portraitUpsideDown:
                direction = .clockwise
            case .landscapeLeft:
                direction = .unknown
            case .landscapeRight:
                direction = .unknown
            case .unknown, .faceUp, .faceDown:
                direction = .unknown
            @unknown default:
                direction = .unknown
            }
        case .landscapeRight:
            switch currentOrientation {
            case .portrait:
                direction = .clockwise
            case .portraitUpsideDown:
                direction = .anticlockwise
            case .landscapeLeft:
                direction = .unknown
            case .landscapeRight:
                direction = .unknown
            case .unknown, .faceUp, .faceDown:
                direction = .unknown
            @unknown default:
                direction = .unknown
            }
        case .faceDown, .faceUp:
            break
        @unknown default:
            break
        }
        
        return direction
    }
}

/// This is not needed for operation, just for a text representation of the
/// orientation in the demo.
extension UIDeviceOrientation {
    var displayValue: String {
        switch self {
        case .unknown:
            "unknown"
        case .portrait:
            "portrait"
        case .portraitUpsideDown:
            "portraitUpsideDown"
        case .landscapeLeft:
            "landscapeLeft"
        case .landscapeRight:
            "landscapeRight"
        case .faceUp:
            "faceUp"
        case .faceDown:
            "faceDown"
        @unknown default:
            "unknown"
        }
    }
}


/// Test View
struct OrientationView: View {
    @State var orientation = OrientationMonitor()
    
    var body: some View {
        VStack {
            Text(orientation.current.displayValue)
            Text(orientation.lastRotation.rawValue)
        }
        .padding()
    }
}

#Preview {
    OrientationView()
}