swiftui-layout-components（SwiftUI 布局组件）

SwiftUI Layout & Components

Layout and component patterns for SwiftUI apps targeting iOS 26+ with Swift 6.3. Covers stack and grid layouts, list patterns, scroll views, forms, controls, search, and overlays. Patterns are backward-compatible to iOS 17 unless noted.

Contents

• Layout Fundamentals
• Grid Layouts
• List Patterns
• ScrollView
• Form and Controls
• Searchable
• Overlay and Presentation
• Common Mistakes
• Review Checklist
• References

Layout Fundamentals

Standard Stacks

Use VStack, HStack, and ZStack for small, fixed-size content. They render all children immediately.

VStack(alignment: .leading) {
    Text(title).font(.headline)
    Text(subtitle).font(.subheadline).foregroundStyle(.secondary)
}

Lazy Stacks

Use LazyVStack and LazyHStack inside ScrollView for large or dynamic collections. They create child views on demand as they scroll into view.

ScrollView {
    LazyVStack {
        ForEach(items) { item in
            ItemRow(item: item)
        }
    }
    .padding(.horizontal)
}

When to use which:

• Non-lazy stacks: Small, fixed content (headers, toolbars, forms with few fields)
• Lazy stacks: Large or unknown-size collections, feeds, chat messages

Grid Layouts

Use LazyVGrid for icon pickers, media galleries, and dense visual selections. Use .adaptive columns for layouts that scale across device sizes, or .flexible columns for a fixed column count.

// Adaptive grid -- columns adjust to fit
let columns = [GridItem(.adaptive(minimum: 120, maximum: 1024))]

LazyVGrid(columns: columns) {
    ForEach(items) { item in
        ThumbnailView(item: item)
            .aspectRatio(1, contentMode: .fit)
    }
}

// Fixed 3-column grid
let columns = Array(repeating: GridItem(.flexible(minimum: 100), spacing: 4), count: 3)

LazyVGrid(columns: columns, spacing: 4) {
    ForEach(items) { item in
        ThumbnailView(item: item)
    }
}

Use .aspectRatio for cell sizing. Never place GeometryReader inside lazy containers -- it forces eager measurement and defeats lazy loading. Use .onGeometryChange (iOS 16+) if you need to read dimensions.

See references/grids.md for full grid patterns and design choices.

List Patterns

Use List for feed-style content and settings rows where built-in row reuse, selection, and accessibility matter.

List {
    Section("General") {
        NavigationLink("Display") { DisplaySettingsView() }
        NavigationLink("Haptics") { HapticsSettingsView() }
    }
    Section("Account") {
        Button("Sign Out", role: .destructive) { }
    }
}
.listStyle(.insetGrouped)

Key patterns:

• .listStyle(.plain) for feed layouts, .insetGrouped for settings
• .scrollContentBackground(.hidden) + custom background for themed surfaces
• .listRowInsets(...) and .listRowSeparator(.hidden) for spacing and separator control
• Use ScrollPosition with .scrollPosition($scrollPosition) for scroll-to-top or jump-to-id
• Use .refreshable {} for pull-to-refresh feeds
• Use .contentShape(Rectangle()) on rows that should be tappable end-to-end

iOS 26: Apply .scrollEdgeEffectStyle(.soft, for:.top) for modern scroll edge effects.

See references/list.md for full list patterns including feed lists with scroll-to-top.

ScrollView

Use ScrollView with lazy stacks when you need custom layout, mixed content, or horizontal scrolling.

ScrollView(.horizontal, showsIndicators: false) {
    LazyHStack {
        ForEach(chips) { chip in
            ChipView(chip: chip)
        }
    }
}

ScrollPosition: Enables declarative, bidirectional scroll position tracking and programmatic scrolling.

@State private var scrollPosition = ScrollPosition(edge: .bottom)

ScrollView {
    LazyVStack {
        ForEach(messages) { message in
            MessageRow(message: message)
        }
    }
    .scrollTargetLayout()
}
.scrollPosition($scrollPosition)
.onChange(of: messages.last?.id) {
    withAnimation { scrollPosition.scrollTo(edge: .bottom) }
}

See references/scrollview.md for full ScrollPosition patterns including scroll-to-id and user-scroll detection.

safeAreaInset(edge:) pins content (input bars, toolbars) above the keyboard without affecting scroll layout.

iOS 26 additions:

• .scrollEdgeEffectStyle(.soft, for:.top) -- fading edge effect
• .backgroundExtensionEffect() -- mirror/blur at safe area edges (use sparingly, one per screen)
• .safeAreaBar(edge:) -- attach bar views that integrate with scroll effects

See references/scrollview.md for full scroll patterns and iOS 26 edge effects.

Form and Controls

Form

Use Form for structured settings and input screens. Group related controls into Section blocks.

Form {
    Section("Notifications") {
        Toggle("Mentions", isOn: $prefs.mentions)
        Toggle("Follows", isOn: $prefs.follows)
    }
    Section("Appearance") {
        Picker("Theme", selection: $theme) {
            ForEach(Theme.allCases, id: \.self) { Text($0.title).tag($0) }
        }
        Slider(value: $fontScale, in: 0.5...1.5, step: 0.1)
    }
}
.formStyle(.grouped)
.scrollContentBackground(.hidden)

Use @FocusState to manage keyboard focus in input-heavy forms. Wrap in NavigationStack only when presented standalone or in a sheet.

Controls

Bind controls directly to @State, @Binding, or @AppStorage. Group related controls in Form sections. Use .disabled(...) to reflect locked or inherited settings. Use Label inside toggles to combine icon + text when it adds clarity.

// Toggle sections
Form {
  Section("Notifications") {
    Toggle("Mentions", isOn: $preferences.notificationsMentionsEnabled)
    Toggle("Follows", isOn: $preferences.notificationsFollowsEnabled)
  }
}

// Slider with value text
Section("Font Size") {
  Slider(value: $fontSizeScale, in: 0.5...1.5, step: 0.1)
  Text("Scale: \(String(format: "%.1f", fontSizeScale))")
}

// Picker for enums
Picker("Default Visibility", selection: $visibility) {
  ForEach(Visibility.allCases, id: \.self) { option in
    Text(option.title).tag(option)
  }
}

Avoid .pickerStyle(.segmented) for large sets; use menu or inline styles. Don't hide labels for sliders; always show context.

See references/form.md for full form examples.

Searchable

Add native search UI with .searchable. Use .searchScopes for multiple modes and .task(id:) for debounced async results.

@MainActor
struct ExploreView: View {
  @State private var searchQuery = ""
  @State private var searchScope: SearchScope = .all
  @State private var isSearching = false
  @State private var results: [SearchResult] = []

  var body: some View {
    List {
      if isSearching {
        ProgressView()
      } else {
        ForEach(results) { result in
          SearchRow(result: result)
        }
      }
    }
    .searchable(
      text: $searchQuery,
      placement: .navigationBarDrawer(displayMode: .always),
      prompt: Text("Search")
    )
    .searchScopes($searchScope) {
      ForEach(SearchScope.allCases, id: \.self) { scope in
        Text(scope.title)
      }
    }
    .task(id: searchQuery) {
      await runSearch()
    }
  }

  private func runSearch() async {
    guard !searchQuery.isEmpty else {
      results = []
      return
    }
    isSearching = true
    defer { isSearching = false }
    try? await Task.sleep(for: .milliseconds(250))
    results = await fetchResults(query: searchQuery, scope: searchScope)
  }
}

Show a placeholder when search is empty. Debounce input to avoid overfetching. Keep search state local to the view. Avoid running searches for empty strings.

Overlay and Presentation

Use .overlay(alignment:) for transient UI (toasts, banners) without affecting layout.

struct AppRootView: View {
  @State private var toast: Toast?

  var body: some View {
    content
      .overlay(alignment: .top) {
        if let toast {
          ToastView(toast: toast)
            .transition(.move(edge: .top).combined(with: .opacity))
            .onAppear {
              Task {
                try? await Task.sleep(for: .seconds(2))
                withAnimation { self.toast = nil }
              }
            }
        }
      }
  }
}

Prefer overlays for transient UI rather than embedding in layout stacks. Use transitions and short auto-dismiss timers. Keep overlays aligned to a clear edge (.top or .bottom). Avoid overlays that block all interaction unless explicitly needed. Don't stack many overlays; use a queue or replace the current toast.

fullScreenCover: Use .fullScreenCover(item:) for immersive presentations that cover the entire screen (media viewers, onboarding flows).

Common Mistakes

1. Using non-lazy stacks for large collections -- causes all children to render immediately
2. Placing GeometryReader inside lazy containers -- defeats lazy loading
3. Using array indices as ForEach IDs -- causes incorrect diffing and UI bugs
4. Nesting scroll views of the same axis -- causes gesture conflicts
5. Heavy custom layouts inside List rows -- use ScrollView + LazyVStack instead
6. Missing .contentShape(Rectangle()) on tappable rows -- tap area is text-only
7. Hard-coding frame dimensions for sheets -- use .presentationSizing instead
8. Running searches on empty strings -- always guard against empty queries
9. Mixing List and ScrollView in the same hierarchy -- gesture conflicts
10. Using .pickerStyle(.segmented) for large option sets -- use menu or inline styles
11. Hard-coding spacing: on stacks and grids by default -- omit to get platform-adaptive spacing; only specify for intentional tight (0–4pt) or wide gaps

Review Checklist

• LazyVStack/LazyHStack used for large or dynamic collections
• Stable Identifiable IDs on all ForEach items (not array indices)
• No GeometryReader inside lazy containers
• List style matches context (.plain for feeds, .insetGrouped for settings)
• Form used for structured input screens (not custom stacks)
• .searchable debounces input with .task(id:)
• .refreshable added where data source supports pull-to-refresh
• Overlays use transitions and auto-dismiss timers
• .contentShape(Rectangle()) on tappable rows
• @FocusState manages keyboard focus in forms
• Stack/grid spacing: omitted unless a specific value is required

References

• Grid patterns: references/grids.md
• List and section patterns: references/list.md
• ScrollView and lazy stacks: references/scrollview.md
• Form patterns: references/form.md
• Architecture and state management: see swiftui-patterns skill
• Navigation patterns: see swiftui-navigation skill