Developing Live Activities for iOS

Developing Live Activities for iOS

Live Activities — iOS 16.1+ feature allowing app to display dynamic content directly on lock screen and Dynamic Island (iPhone 14 Pro+). Taxi coming to you — progress bar on Lock Screen updates in real time. Match in progress — score in Dynamic Island without unlocking phone.

Live up to 8 hours (or 12 with explicit extension via ActivityKit), then system dismisses them. After 12 hours — forced termination.

ActivityKit: Architecture

Live Activity built on three things: ActivityAttributes (static data set on start), ContentState (dynamic data updated via push or API), and SwiftUI View for three representations: Lock Screen / Standby, Dynamic Island Compact, Dynamic Island Expanded.

struct DeliveryAttributes: ActivityAttributes {
    // Static — doesn't change during life
    let orderId: String
    let restaurantName: String

    struct ContentState: Codable, Hashable {
        // Dynamic — updates
        var status: DeliveryStatus
        var estimatedMinutes: Int
        var courierLocation: CLLocationCoordinate2D?
    }
}

Start from app:

let attributes = DeliveryAttributes(orderId: "1234", restaurantName: "South Pizza")
let state = DeliveryAttributes.ContentState(status: .preparing, estimatedMinutes: 30)
let content = ActivityContent(state: state, staleDate: Date().addingTimeInterval(600))

let activity = try Activity.request(
    attributes: attributes,
    content: content,
    pushType: .token  // Get push token for remote updates
)

staleDate — date after which content is stale and system can show outdatedness indicator. For taxi: Date() + estimatedMinutes * 60.

Update via Push Notifications

Most reliable way to update Live Activity from server — ActivityKit Push Notifications (not regular APNs).

Push payload:

{
  "aps": {
    "timestamp": 1698765432,
    "event": "update",
    "content-state": {
      "status": "in_delivery",
      "estimatedMinutes": 12
    },
    "alert": {
      "title": "Courier left",
      "body": "Expect in 12 minutes"
    }
  }
}

event: "end" — terminate Live Activity via push. alert in push for Live Activity — displayed as Dynamic Island update with haptic feedback.

Push token for Live Activity differs from regular APNs token. Get via activity.pushTokenUpdates AsyncSequence: need to listen for updates, token can change.

Task {
    for await tokenData in activity.pushTokenUpdates {
        let token = tokenData.map { String(format: "%02x", $0) }.joined()
        await sendTokenToServer(token)
    }
}

SwiftUI Views for Different Zones

struct DeliveryLiveActivityView: View {
    let context: ActivityViewContext<DeliveryAttributes>

    var body: some View {
        // Lock Screen / StandBy
        HStack {
            Image(systemName: statusIcon(context.state.status))
            VStack(alignment: .leading) {
                Text(context.attributes.restaurantName)
                    .font(.headline)
                Text("~\(context.state.estimatedMinutes) min")
                    .font(.subheadline)
            }
            Spacer()
            DeliveryProgressView(status: context.state.status)
        }
        .padding()
    }
}

DynamicIsland builder for Dynamic Island:

DynamicIsland {
    // Expanded — long tap
    DynamicIslandExpandedRegion(.leading) {
        Image(systemName: "bicycle")
    }
    DynamicIslandExpandedRegion(.trailing) {
        Text("\(context.state.estimatedMinutes) min")
    }
    DynamicIslandExpandedRegion(.bottom) {
        Text("Courier: \(courierName)")
    }
} compactLeading: {
    Image(systemName: "bicycle")
} compactTrailing: {
    Text("\(context.state.estimatedMinutes)m")
} minimal: {
    Image(systemName: "bicycle")
}

Compact — two zones beside "island" in collapsed state. Minimal — one small icon when multiple Live Activities active.

Constraints to Know

ContentState size — max 4KB in ActivityKit push payload. For courier coordinates: don't send entire track, only current position.

App must be foreground or have Background Push to start Live Activity. Can't start from background without user action (from iOS 17.2 — can via ActivityAuthorizationInfo().areActivitiesEnabled).

Simulator supports Live Activities from iOS 16.2 Simulator. Dynamic Island — only on physical iPhone 14 Pro/Pro Max and newer.

Timeframe: 3-5 days for basic implementation with push-updates. Cost depends on UI complexity and server part presence.