live-activities（现场活动）

Live Activities and Dynamic Island

Build real-time, glanceable experiences on the Lock Screen, Dynamic Island, StandBy, CarPlay, and Mac menu bar using ActivityKit. Patterns target iOS 26+ with Swift 6.2, backward-compatible to iOS 16.1 unless noted.

See references/live-activity-patterns.md for complete code patterns including push payload formats, concurrent activities, state observation, and testing.

Contents

• Workflow
• ActivityAttributes Definition
• Activity Lifecycle
• Lock Screen Presentation
• Dynamic Island
• Push-to-Update
• iOS 26 Additions
• Common Mistakes
• Review Checklist
• References

Workflow

1. Create a new Live Activity

1. Add NSSupportsLiveActivities = YES to the host app's Info.plist.
2. Define an ActivityAttributes struct with a nested ContentState.
3. Create an ActivityConfiguration in the widget bundle with Lock Screen content and Dynamic Island closures.
4. Start the activity with Activity.request(attributes:content:pushType:).
5. Update with activity.update(_:) and end with activity.end(_:dismissalPolicy:).
6. Forward push tokens to your server for remote updates.

2. Review existing Live Activity code

Run through the Review Checklist at the end of this document.

ActivityAttributes Definition

Define both static data (immutable for the activity lifetime) and dynamic ContentState (changes with each update). Keep ContentState small because the entire struct is serialized on every update and push payload.

import ActivityKit

struct DeliveryAttributes: ActivityAttributes {
    // Static -- set once at activity creation, never changes
    var orderNumber: Int
    var restaurantName: String

    // Dynamic -- updated throughout the activity lifetime
    struct ContentState: Codable, Hashable {
        var driverName: String
        var estimatedDeliveryTime: ClosedRange<Date>
        var currentStep: DeliveryStep
    }
}

enum DeliveryStep: String, Codable, Hashable, CaseIterable {
    case confirmed, preparing, pickedUp, delivering, delivered

    var icon: String {
        switch self {
        case .confirmed: "checkmark.circle"
        case .preparing: "frying.pan"
        case .pickedUp: "bag.fill"
        case .delivering: "box.truck.fill"
        case .delivered: "house.fill"
        }
    }
}

Stale Date

Set staleDate on ActivityContent to tell the system when content becomes outdated. The system sets context.isStale to true after this date; show fallback UI (e.g., "Updating...") in your views.

let content = ActivityContent(
    state: state,
    staleDate: Date().addingTimeInterval(300), // stale after 5 minutes
    relevanceScore: 75
)

Activity Lifecycle

Starting

Use Activity.request to create and display a Live Activity. Pass .token as the pushType to enable remote updates via APNs.

let attributes = DeliveryAttributes(orderNumber: 42, restaurantName: "Pizza Place")
let state = DeliveryAttributes.ContentState(
    driverName: "Alex",
    estimatedDeliveryTime: Date()...Date().addingTimeInterval(1800),
    currentStep: .preparing
)
let content = ActivityContent(state: state, staleDate: nil, relevanceScore: 75)

do {
    let activity = try Activity.request(
        attributes: attributes,
        content: content,
        pushType: .token
    )
    print("Started activity: \(activity.id)")
} catch {
    print("Failed to start activity: \(error)")
}

Updating

Update the dynamic content state from the app. Use AlertConfiguration to trigger a visible banner and sound alongside the update.

let updatedState = DeliveryAttributes.ContentState(
    driverName: "Alex",
    estimatedDeliveryTime: Date()...Date().addingTimeInterval(600),
    currentStep: .delivering
)
let updatedContent = ActivityContent(
    state: updatedState,
    staleDate: Date().addingTimeInterval(300),
    relevanceScore: 90
)

// Silent update
await activity.update(updatedContent)

// Update with an alert
await activity.update(updatedContent, alertConfiguration: AlertConfiguration(
    title: "Order Update",
    body: "Your driver is nearby!",
    sound: .default
))

Ending

End the activity when the tracked event completes. Choose a dismissal policy to control how long the ended activity lingers on the Lock Screen.

let finalState = DeliveryAttributes.ContentState(
    driverName: "Alex",
    estimatedDeliveryTime: Date()...Date(),
    currentStep: .delivered
)
let finalContent = ActivityContent(state: finalState, staleDate: nil, relevanceScore: 0)

// System decides when to remove (up to 4 hours)
await activity.end(finalContent, dismissalPolicy: .default)

// Remove immediately
await activity.end(finalContent, dismissalPolicy: .immediate)

// Remove after a specific time (max 4 hours from now)
await activity.end(finalContent, dismissalPolicy: .after(Date().addingTimeInterval(3600)))

Always end activities on all code paths -- success, error, and cancellation. A leaked activity stays on the Lock Screen until the system kills it (up to 8 hours), which frustrates users.

Lock Screen Presentation

The Lock Screen is the primary surface for Live Activities. Every device with iOS 16.1+ displays Live Activities here. Design this layout first.

struct DeliveryActivityWidget: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: DeliveryAttributes.self) { context in
            // Lock Screen / StandBy / CarPlay / Mac menu bar content
            VStack(alignment: .leading, spacing: 8) {
                HStack {
                    Text(context.attributes.restaurantName)
                        .font(.headline)
                    Spacer()
                    Text("Order #\(context.attributes.orderNumber)")
                        .font(.caption)
                        .foregroundStyle(.secondary)
                }

                if context.isStale {
                    Label("Updating...", systemImage: "arrow.trianglehead.2.clockwise")
                        .font(.subheadline)
                        .foregroundStyle(.secondary)
                } else {
                    HStack {
                        Label(context.state.driverName, systemImage: "person.fill")
                        Spacer()
                        Text(timerInterval: context.state.estimatedDeliveryTime,
                             countsDown: true)
                            .monospacedDigit()
                    }
                    .font(.subheadline)

                    // Progress steps
                    HStack(spacing: 12) {
                        ForEach(DeliveryStep.allCases, id: \.self) { step in
                            Image(systemName: step.icon)
                                .foregroundStyle(
                                    step <= context.state.currentStep ? .primary : .tertiary
                                )
                        }
                    }
                }
            }
            .padding()
        } dynamicIsland: { context in
            // Dynamic Island closures (see next section)
            DynamicIsland {
                // Expanded regions...
                DynamicIslandExpandedRegion(.leading) {
                    Image(systemName: "box.truck.fill").font(.title2)
                }
                DynamicIslandExpandedRegion(.trailing) {
                    Text(timerInterval: context.state.estimatedDeliveryTime,
                         countsDown: true)
                        .font(.caption).monospacedDigit()
                }
                DynamicIslandExpandedRegion(.center) {
                    Text(context.attributes.restaurantName).font(.headline)
                }
                DynamicIslandExpandedRegion(.bottom) {
                    HStack(spacing: 12) {
                        ForEach(DeliveryStep.allCases, id: \.self) { step in
                            Image(systemName: step.icon)
                                .foregroundStyle(
                                    step <= context.state.currentStep ? .primary : .tertiary
                                )
                        }
                    }
                }
            } compactLeading: {
                Image(systemName: "box.truck.fill")
            } compactTrailing: {
                Text(timerInterval: context.state.estimatedDeliveryTime,
                     countsDown: true)
                    .frame(width: 40).monospacedDigit()
            } minimal: {
                Image(systemName: "box.truck.fill")
            }
        }
    }
}

Lock Screen Sizing

The Lock Screen presentation has limited vertical space. Avoid layouts taller than roughly 160 points. Use supplementalActivityFamilies to opt into .small (compact) or .medium (standard) sizing:

ActivityConfiguration(for: DeliveryAttributes.self) { context in
    // Lock Screen content
} dynamicIsland: { context in
    // Dynamic Island
}
.supplementalActivityFamilies([.small, .medium])

Dynamic Island

The Dynamic Island is available on iPhone 14 Pro and later. It has three presentation modes. Design all three, but treat the Lock Screen as the primary surface since not all devices have a Dynamic Island.

Compact (Leading + Trailing)

Always visible when a single Live Activity is active. Space is extremely limited -- show only the most critical information.

Minimal

Shown when multiple Live Activities compete for space. Only one activity gets the minimal slot. Display a single icon or glyph.

Expanded Regions

Shown when the user long-presses the Dynamic Island.

Keyline Tint

Apply a subtle tint to the Dynamic Island border:

DynamicIsland { /* expanded */ }
    compactLeading: { /* ... */ }
    compactTrailing: { /* ... */ }
    minimal: { /* ... */ }
    .keylineTint(.blue)

Push-to-Update

Push-to-update sends Live Activity updates through APNs, which is more efficient than polling from the app and works when the app is suspended.

Setup

Pass .token as the pushType when starting the activity, then forward the push token to your server:

let activity = try Activity.request(
    attributes: attributes,
    content: content,
    pushType: .token
)

// Observe token changes -- tokens can rotate
Task {
    for await token in activity.pushTokenUpdates {
        let tokenString = token.map { String(format: "%02x", $0) }.joined()
        try await ServerAPI.shared.registerActivityToken(
            tokenString, activityID: activity.id
        )
    }
}

APNs Payload Format

Send an HTTP/2 POST to APNs with these headers and JSON body:

Required HTTP headers:

• apns-push-type: liveactivity
• apns-topic: <bundle-id>.push-type.liveactivity
• apns-priority: 5 (low) or 10 (high, triggers alert)

Update payload:

{
    "aps": {
        "timestamp": 1700000000,
        "event": "update",
        "content-state": {
            "driverName": "Alex",
            "estimatedDeliveryTime": {
                "lowerBound": 1700000000,
                "upperBound": 1700001800
            },
            "currentStep": "delivering"
        },
        "stale-date": 1700000300,
        "alert": {
            "title": "Delivery Update",
            "body": "Your driver is nearby!"
        }
    }
}

End payload: Same structure with "event": "end" and optional "dismissal-date".

The content-state JSON must match the ContentState Codable structure exactly. Mismatched keys or types cause silent failures.

Push-to-Start

Start a Live Activity remotely without the app running (iOS 17.2+):

Task {
    for await token in Activity<DeliveryAttributes>.pushToStartTokenUpdates {
        let tokenString = token.map { String(format: "%02x", $0) }.joined()
        try await ServerAPI.shared.registerPushToStartToken(tokenString)
    }
}

Frequent Push Updates

Add NSSupportsLiveActivitiesFrequentUpdates = YES to Info.plist to increase the push update budget. Use for activities that update more than once per minute (sports scores, ride tracking).

iOS 26 Additions

Scheduled Live Activities (iOS 26+)

Schedule a Live Activity to start at a future time. The system starts the activity automatically without the app being in the foreground. Use for events with known start times (sports games, flights, scheduled deliveries).

let scheduledDate = Calendar.current.date(
    from: DateComponents(year: 2026, month: 3, day: 15, hour: 19, minute: 0)
)!

let activity = try Activity.request(
    attributes: attributes,
    content: content,
    pushType: .token,
    start: scheduledDate
)

ActivityStyle (iOS 16.1+ type, style: parameter iOS 26+)

Control persistence: .standard (persists until ended, default) or .transient (system may dismiss automatically). Use .transient for short-lived updates like transit arrivals. The style: parameter on Activity.request requires iOS 26+.

let activity = try Activity.request(
    attributes: attributes, content: content,
    pushType: .token, style: .transient
)

Mac Menu Bar & CarPlay (iOS 26+)

Live Activities automatically appear in macOS Tahoe menu bar (via iPhone Mirroring) and CarPlay Home Screen. No additional code needed — ensure Lock Screen layout is legible at smaller scales.

Channel-Based Push (iOS 18+)

Broadcast updates to many Live Activities at once with .channel:

let activity = try Activity.request(
    attributes: attributes, content: content,
    pushType: .channel("delivery-updates")
)

Common Mistakes

DON'T: Put too much content in the compact presentation -- it is tiny. DO: Show only the most critical info (icon + one value) in compact leading/trailing.

DON'T: Update Live Activities too frequently from the app (drains battery). DO: Use push-to-update for server-driven updates. Limit app-side updates to user actions.

DON'T: Forget to end the activity when the event completes. DO: Always end activities on success, error, and cancellation paths. A leaked activity frustrates users.

DON'T: Assume the Dynamic Island is available (only iPhone 14 Pro+). DO: Design for the Lock Screen as the primary surface; Dynamic Island is supplementary.

DON'T: Store sensitive information in ActivityAttributes (visible on Lock Screen). DO: Keep sensitive data in the app and show only safe-to-display summaries.

DON'T: Forget to handle stale dates. DO: Check context.isStale in views and show fallback UI ("Updating..." or similar).

DON'T: Ignore push token rotation. Tokens can change at any time. DO: Use activity.pushTokenUpdates async sequence and re-register on every emission.

DON'T: Forget the NSSupportsLiveActivities Info.plist key. DO: Add NSSupportsLiveActivities = YES to the host app's Info.plist (not the extension).

DON'T: Use the deprecated contentState-based API for request/update/end. DO: Use ActivityContent for all lifecycle calls.

DON'T: Put heavy logic in Live Activity views. They render in a size-limited widget process. DO: Pre-compute display values and pass them through ContentState.

Review Checklist

• ActivityAttributes defines static properties and ContentState
• NSSupportsLiveActivities = YES in host app Info.plist
• Activity uses ActivityContent (not deprecated contentState API)
• Activity ended in all code paths (success, error, cancellation)
• Lock Screen layout handles context.isStale
• Dynamic Island compact, expanded, and minimal implemented
• Push token forwarded to server via activity.pushTokenUpdates
• AlertConfiguration used for important updates
• ActivityAuthorizationInfo checked before starting
• ContentState kept small (serialized on every update)
• Tested on device (Dynamic Island differs from Simulator)
• Ensure ActivityAttributes and ContentState types are Sendable; update Live Activity UI on @MainActor

References

• See references/live-activity-patterns.md for patterns and code examples