为折叠屏 iPhone Duo 做准备：iOS 应用需要重构的五个界面假设

import SwiftUI

@main
struct DuoReadyApp: App {
    var body: some Scene {
        WindowGroup {
            AdaptiveCatalogView()
        }
    }
}

struct CatalogItem: Identifiable, Hashable {
    let id = UUID()
    let title: String
    let detail: String
}

struct AdaptiveCatalogView: View {
    private static let items = [
        CatalogItem(title: "相机", detail: "检查预览裁剪、旋转和权限状态。"),
        CatalogItem(title: "地图", detail: "验证列表与地图在宽屏下的协作。"),
        CatalogItem(title: "编辑器", detail: "确保键盘出现后主要操作仍然可见。")
    ]

    @Environment(\.horizontalSizeClass) private var horizontalSizeClass
    @State private var selection: CatalogItem.ID?

    var body: some View {
        GeometryReader { proxy in
            let showTwoColumns = horizontalSizeClass == .regular && proxy.size.width >= 700

            Group {
                if showTwoColumns {
                    NavigationSplitView {
                        List(Self.items, selection: $selection) { item in
                            Text(item.title)
                                .tag(item.id)
                        }
                        .navigationTitle("功能")
                    } detail: {
                        if let item = selectedItem {
                            DetailView(item: item)
                        } else {
                            ContentUnavailableView(
                                "请选择一个功能",
                                systemImage: "rectangle.split.2x1"
                            )
                        }
                    }
                } else {
                    NavigationStack {
                        List(Self.items) { item in
                            NavigationLink(value: item) {
                                Text(item.title)
                            }
                        }
                        .navigationTitle("功能")
                        .navigationDestination(for: CatalogItem.self) { item in
                            DetailView(item: item)
                        }
                    }
                }
            }
            .safeAreaInset(edge: .bottom) {
                BottomActionBar()
            }
            .animation(.snappy, value: showTwoColumns)
        }
    }

    private var selectedItem: CatalogItem? {
        Self.items.first { $0.id == selection }
    }
}

struct DetailView: View {
    let item: CatalogItem

    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 16) {
                Text(item.title)
                    .font(.largeTitle.bold())
                Text(item.detail)
                    .font(.body)
                Text("改变窗口宽度，观察导航结构如何切换。")
                    .foregroundStyle(.secondary)
            }
            .frame(maxWidth: 720, alignment: .leading)
            .padding()
        }
        .navigationTitle(item.title)
        .navigationBarTitleDisplayMode(.inline)
    }
}

struct BottomActionBar: View {
    var body: some View {
        Button("创建新项目", systemImage: "plus") {
            print("Create tapped")
        }
        .buttonStyle(.borderedProminent)
        .frame(maxWidth: .infinity)
        .padding()
        .background(.bar)
    }
}

import AVFoundation
import UIKit

final class CameraPreviewView: UIView {
    override class var layerClass: AnyClass {
        AVCaptureVideoPreviewLayer.self
    }

    var previewLayer: AVCaptureVideoPreviewLayer {
        guard let layer = layer as? AVCaptureVideoPreviewLayer else {
            fatalError("Unexpected backing layer")
        }
        return layer
    }

    func attach(session: AVCaptureSession) {
        previewLayer.session = session
        previewLayer.videoGravity = .resizeAspectFill
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        previewLayer.frame = bounds
    }
}

.ignoresSafeArea()

rg 'UIScreen\.main|statusBarFrame|keyWindow|ignoresSafeArea|UIDevice\.current' \
  --glob '*.swift' .