SwiftUI - Determining Current Device and Orientation

问题

I am trying to detect when the device is on iPad and in Portrait.

Currently I use the UIDevice API in UIKit and use an environment object to watch changes. I use the solution found here - Determining Current Device and Orientation.

However the orientationInfo.orientation is initially always equal to .portrait until rotated into portrait and then back to landscape.

So when doing the following to display the FABView

struct HomeView: View {

@EnvironmentObject var orientationInfo: OrientationInfo
let isPhone = UIDevice.current.userInterfaceIdiom == .phone

    var body: some View {
      ZStack(alignment: .bottom) {
          #if os(iOS)
          if isPhone == false && orientationInfo.orientation == .portrait {
            FABView()
          }
          #endif
      }
    }
}

The view is loaded when the iPad is initially in landscape, but when changing to portrait and back to landscape is then removed. Why is this happening and how can I make sure the view isn't loaded on first load ?

Full Code

struct HomeTab: View {
    
    var body: some View {
        NavigationView {
            HomeView()
                .environmentObject(OrientationInfo())
        }
    }
}

struct HomeView: View {

@EnvironmentObject var orientationInfo: OrientationInfo
let isPhone = UIDevice.current.userInterfaceIdiom == .phone

    var body: some View {
      ZStack(alignment: .bottom) {
          #if os(iOS)
          if isPhone == false && orientationInfo.orientation == .portrait {
            FABView()
          }
          #endif
      }
    }
}

final class OrientationInfo: ObservableObject {
    enum Orientation {
        case portrait
        case landscape
    }
    
    @Published var orientation: Orientation
    
    private var _observer: NSObjectProtocol?
    
    init() {
        // fairly arbitrary starting value for 'flat' orientations
        if UIDevice.current.orientation.isLandscape {
            self.orientation = .landscape
        }
        else {
            self.orientation = .portrait
        }
        
        // unowned self because we unregister before self becomes invalid
        _observer = NotificationCenter.default.addObserver(forName: UIDevice.orientationDidChangeNotification, object: nil, queue: nil) { [unowned self] note in
            guard let device = note.object as? UIDevice else {
                return
            }
            if device.orientation.isPortrait {
                self.orientation = .portrait
            }
            else if device.orientation.isLandscape {
                self.orientation = .landscape
            }
        }
    }
    
    deinit {
        if let observer = _observer {
            NotificationCenter.default.removeObserver(observer)
        }
    }
}

回答1:

You can use UIDevice.orientationDidChangeNotification for detecting orientation changes but you shouldn't rely on it when the app starts.

UIDevice.current.orientation.isValidInterfaceOrientation will be false at the beginning and therefore both

UIDevice.current.orientation.isLandscape

and

UIDevice.current.orientation.isPortrait

will return false.

Instead you can use interfaceOrientation from the first window scene:

struct ContentView: View {
    @State private var isPortrait = false
    
    var body: some View {
        Text("isPortrait: \(String(isPortrait))")
            .onReceive(NotificationCenter.default.publisher(for: UIDevice.orientationDidChangeNotification)) { _ in
                guard let scene = UIApplication.shared.windows.first?.windowScene else { return }
                self.isPortrait = scene.interfaceOrientation.isPortrait
            }
    }
}

Also note that device orientation is not equal to interface orientation. When the device is upside down in portrait mode, device orientation is portrait but interface orientation can be landscape as well.

I think it's better to rely on the interface orientation in your case.

来源：https://stackoverflow.com/questions/65573508/swiftui-determining-current-device-and-orientation

标签

ios

swiftui

uikit