SwiftUI - 确定电流设备和方向

Question

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)
        }
    }
}

Answer 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.