SwiftUI - 确定当前设备和方向

Question

我正在尝试检测设备何时在 iPad 上且处于纵向状态。

目前我使用UIDeviceUIKit 中的 API 并使用环境对象来观察变化。我使用此处找到的解决方案 -确定当前设备和方向.

然而orientationInfo.orientation最初总是等于.portrait until rotated into portrait and then back to landscape.

因此，当执行以下操作来显示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
      }
    }
}

当 iPad 最初处于横向时，会加载该视图，但当更改为纵向并返回横向时，该视图会被删除。为什么会发生这种情况？如何确保第一次加载时未加载视图？

完整代码

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

您可以用于UIDevice.orientationDidChangeNotification检测方向变化，但应用程序启动时不应依赖它。

UIDevice.current.orientation.isValidInterfaceOrientation一开始就是假的，因此两者

• UIDevice.current.orientation.isLandscape

和

• UIDevice.current.orientation.isPortrait

将返回false。

interfaceOrientation相反，您可以从第一个窗口场景中使用：

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
            }
    }
}

另请注意，设备方向不等于界面方向。当设备在纵向模式下倒置时，设备方向为纵向，但界面方向也可以为横向。

我认为在您的情况下最好依靠界面方向。