Extensions & Widgets

Widget development patterns for Home Screen, Lock Screen, StandBy, Live Activities, and Control Center controls. Covers timeline management, data sharing between app and extensions, and extension lifecycle.

When to Use This Skill

Use this skill when you're:

• Implementing any widget (Home Screen, Lock Screen, StandBy, Control Center)
• Creating Live Activities with Dynamic Island
• Widget shows stale data or doesn't update
• Widget not appearing in gallery
• Interactive buttons not responding
• Live Activity fails to start
• Control Center control is unresponsive
• Sharing data between main app and widget

Mental model: Widgets are archived snapshots on a timeline, not live views. They render, get archived, and the system displays the snapshot.

Example Prompts

Questions you can ask Claude that will draw from this skill:

• "My widget isn't updating even after I change data in the main app."
• "How do I share data between my app and widget?"
• "Widget shows old data even after I update the app."
• "Live Activity fails to start with no error message."
• "Control Center control takes forever to respond."
• "Interactive widget button does nothing when tapped."
• "Widget gallery doesn't show my widget."

What's Covered

Timeline Management

• TimelineProvider patterns (getTimeline, getSnapshot, placeholder)
• Refresh budgets and policies
• Manual reload with WidgetCenter
• When widgets actually update

Data Sharing

• App Groups entitlement setup
• Shared UserDefaults with suite name
• Container URLs for file sharing
• Why widgets can't see main app data directly

Live Activities

• ActivityAttributes and 4KB data limit
• Dynamic Island presentation
• Push notification updates
• Authorization and entitlements

Control Center Controls (iOS 18+)

• ValueProvider for async state
• Optimistic UI patterns
• Control action handling

Interactive Widgets (iOS 17+)

• App Intent integration
• Button/Toggle in widget views
• perform() implementation
• WidgetCenter reload after actions

Common Anti-Patterns

• Network calls in widget view (use TimelineProvider)
• Missing App Groups entitlement
• Wrong UserDefaults suite name
• Forgetting WidgetCenter.shared.reloadAllTimelines()

Key Pattern

Data Sharing Between App and Widget

// 1. Add App Groups entitlement to BOTH targets
// Capabilities → App Groups → group.com.yourapp.shared

// 2. Use shared UserDefaults (NOT .standard)
let sharedDefaults = UserDefaults(suiteName: "group.com.yourapp.shared")
sharedDefaults?.set(value, forKey: "myKey")

// 3. Reload widget after data changes
WidgetCenter.shared.reloadAllTimelines()

// ❌ WRONG — Widget can't see this
UserDefaults.standard.set(value, forKey: "key")

Timeline Provider Pattern

struct Provider: TimelineProvider {
    func getTimeline(in context: Context, completion: @escaping (Timeline<Entry>) -> Void) {
        // ✅ Fetch data here (TimelineProvider has network access)
        let data = fetchFromSharedDefaults()

        let entry = SimpleEntry(date: Date(), data: data)
        let timeline = Timeline(entries: [entry], policy: .after(Date().addingTimeInterval(3600)))
        completion(timeline)
    }
}

// ❌ WRONG — Widget view has no network access
struct WidgetView: View {
    var body: some View {
        Text("").onAppear {
            URLSession.shared.data(from: url) // Won't work!
        }
    }
}

Documentation Scope

This page documents the axiom-extensions-widgets skill—widget development patterns Claude uses when you're implementing Home Screen widgets, Live Activities, or Control Center controls.

For comprehensive API reference: See extensions-widgets-ref for complete API coverage, troubleshooting, and expert review checklist.

For App Intents: See app-intents-ref for interactive widget button implementation.

Related

• extensions-widgets-ref — Complete API reference, troubleshooting, expert checklist
• app-intents-ref — App Intents for interactive widgets
• swift-concurrency — Async patterns for data fetching
• swiftdata — Using SwiftData with App Groups

Resources

WWDC: 2025-278, 2024-10157, 2024-10068, 2023-10028, 2023-10194

Docs: /widgetkit, /activitykit, /widgetkit/controlling-interactivity-and-appearance