Meet ActivityKit

import ActivityKit

struct AdventureAttributes: ActivityAttributes {
    let hero: EmojiRanger

    struct ContentState: Codable & Hashable {
        let currentHealthLevel: Double
        let eventDescription: String
    }
}

let adventure = AdventureAttributes(hero: hero)

let initialState = AdventureAttributes.ContentState(
    currentHealthLevel: hero.healthLevel,
    eventDescription: "Adventure has begun!"
)
let content = ActivityContent(state: initialState, staleDate: nil, relevanceScore: 0.0)

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

let heroName = activity.attributes.hero.name               
let contentState = AdventureAttributes.ContentState(
    currentHealthLevel: hero.healthLevel,
    eventDescription: "\(heroName) has taken a critical hit!"
)

var alertConfig = AlertConfiguration(
    title: "\(heroName) has taken a critical hit!",
    body: "Open the app and use a potion to heal \(heroName)",
    sound: .default
)  
     
activity.update(
    ActivityContent<AdventureAttributes.ContentState>(
        state: contentState,
        staleDate: nil
    ),
    alertConfiguration: alertConfig
)

// Observe activity state asynchronously
func observeActivity(activity: Activity<AdventureAttributes>) {
    Task {
        for await activityState in activity.activityStateUpdates {
            if activityState == .dismissed {
                self.cleanUpDismissedActivity()
            }
        }
    }
}

// Observe activity state synchronously
let activityState = activity.activityState
if activityState == .dismissed {
    self.cleanUpDismissedActivity()
}

let hero = activity.attributes.hero

let finalContent = AdventureAttributes.ContentState(
    currentHealthLevel: hero.healthLevel,
    eventDescription: "Adventure over! \(hero.name) has defeated the boss! Congrats!"
)

let dismissalPolicy: ActivityUIDismissalPolicy = .default

activity.end(
    ActivityContent(state: finalContent, staleDate: nil),
    dismissalPolicy: dismissalPolicy)
}

import WidgetKit
import SwiftUI

@main
struct EmojiRangersWidgetBundle: WidgetBundle {
    var body: some Widget {
        EmojiRangerWidget()
        LeaderboardWidget()
        AdventureActivityConfiguration()
    }
}

struct AdventureActivityConfiguration: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: AdventureAttributes.self) { context in
            AdventureLiveActivityView(
                hero: context.attributes.hero,
                isStale: context.isStale,
                contentState: context.state
            )
            .activityBackgroundTint(Color.navyBlue)
        } dynamicIsland: { context in
            // ...
        }
    }
}

struct AdventureActivityConfiguration: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: AdventureAttributes.self) { context in
            // ...
        } dynamicIsland: { context in
            DynamicIsland {
                // ...
            } compactLeading: {
                Avatar(hero: context.attributes.hero)
            } compactTrailing: {
                ProgressView(value: context.state.currentHealthLevel) {
                    Text("\(Int(context.state.currentHealthLevel * 100))")
                }
                .progressViewStyle(.circular)
                .tint(context.state.currentHealthLevel <= 0.2 ? Color.red : Color.green)
            } minimal: {
                // ...
            }
        }
    }
}

struct AdventureActivityConfiguration: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: AdventureAttributes.self) { context in
            // ...
        } dynamicIsland: { context in
            DynamicIsland {
                // ...
            } compactLeading: {
                // ...
            } compactTrailing: {
                // ...
            } minimal: {
                ProgressView(value: context.state.currentHealthLevel) {
                    Avatar(hero: context.attributes.hero)
                }
                .progressViewStyle(.circular)
                .tint(context.state.currentHealthLevel <= 0.2 ? Color.red : Color.green)
            }
        }
    }
}

struct AdventureActivityConfiguration: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: AdventureAttributes.self) { context in
            // ...
        } dynamicIsland: { context in
            DynamicIsland {
                // Leading region
                DynamicIslandExpandedRegion(.leading) {
                    LiveActivityAvatarView(hero: hero)
                }

                // Expanded region
                DynamicIslandExpandedRegion(.trailing) {
                    StatsView(hero: hero, isStale: isStale)
                }

                // Bottom region
                DynamicIslandExpandedRegion(.bottom) {
                    HealthBar(currentHealthLevel: contentState.currentHealthLevel)
                    EventDescriptionView(hero: hero, contentState: contentState)
                }
            } compactLeading: {
                // ...
            } compactTrailing: {
                // ...
            } minimal: {
                // ...
            }
        }
    }
}