iPad端NavigationSplitView侧边栏状态持久化控制问题求助

问题根源 #

你的代码逻辑本身没有问题，但在iOS 18及更早版本中，NavigationSplitView存在系统级bug：绑定的columnVisibility在设备旋转时无法正确保留状态，导致侧边栏可见性被强制重置。而**iOS 26+**官方已修复此问题，你的原始代码在该版本下可正常工作。

兼容旧版本的临时修复方案 #

方案1：用@AppStorage持久化状态 #

将状态存储到UserDefaults，避免视图重建时丢失：

import SwiftUI

@main
struct TestApp: App {
    @AppStorage("splitViewVisibility") private var visibilityRaw = "all"
    
    private var columnVisibility: Binding<NavigationSplitViewVisibility> {
        Binding(
            get: {
                switch visibilityRaw {
                case "all": return .all
                case "detailOnly": return .detailOnly
                default: return .all
                }
            },
            set: {
                switch $0 {
                case .all: visibilityRaw = "all"
                case .detailOnly: visibilityRaw = "detailOnly"
                default: visibilityRaw = "all"
                }
            }
        )
    }

    var body: some Scene {
        WindowGroup {
            NavigationSplitView(columnVisibility: columnVisibility) {
                Color.green
            } detail: {
                LinearGradient(colors: [.red, .yellow], startPoint: .leading, endPoint: .trailing)
            }
            .navigationSplitViewStyle(.balanced)
        }
    }
}

方案2：用ObservableObject管理全局状态 #

创建独立的状态管理器，脱离视图生命周期：

import SwiftUI

class SplitViewState: ObservableObject {
    @Published var columnVisibility: NavigationSplitViewVisibility = .all
}

@main
struct TestApp: App {
    @StateObject private var splitState = SplitViewState()

    var body: some Scene {
        WindowGroup {
            NavigationSplitView(columnVisibility: $splitState.columnVisibility) {
                Color.green
            } detail: {
                LinearGradient(colors: [.red, .yellow], startPoint: .leading, endPoint: .trailing)
            }
            .navigationSplitViewStyle(.balanced)
        }
    }
}

补充：添加手动切换按钮 #

要让用户能通过默认按钮控制侧边栏，需在侧边栏视图中添加工具栏按钮：

// 替换侧边栏的Color.green为以下内容
NavigationStack {
    Color.green
        .toolbar {
            ToolbarItem(placement: .navigationBarTrailing) {
                Button {
                    splitState.columnVisibility = splitState.columnVisibility == .all ? .detailOnly : .all
                } label: {
                    Image(systemName: "sidebar.left")
                }
            }
        }
}

内容的提问来源于stack exchange，提问作者Roberto