Start and Update iOS Live Activities With Broadcast Push Notifications ​

The forth part of a series on Live Activities.

  1. What are iOS Live Activities and Four Kinds of Presentations
  2. Add Live Activities to Your iOS App in 5 Steps
  3. Start and Update iOS Live Activities With Push Notifications
  4. Start and Update iOS Live Activities With Broadcast Push Notifications

Starting with iOS 18 and iPadOS 18, users can subcribe on a channel, then you can send a single broadcast push notification to update all their live activities, rather than sending multiple push notifications using each individual's device token.

Step0: Main flow ​

The figure below describes the main flow:

  1. Your server communicates with Apple Push Notification service(APNs) to create a channel and get a channel ID.

Then, there are two approaches to create a Live Activity that subscribes for broadcast push notification.

  1. Your server sends this channel ID to your app, and then your app use this channel ID to create a Live Activity by code that subscribes for broadcast push notifications on this channel.
  2. Your server sends a push-to-start notification with the channle ID, and then the system will create a Live Activity for you that subscribes for broadcast push notifications on this channel.

sending-channel-management-requests

Step1: Enable broad capability in your AppID ​

Signing on to developer.apple.com.

  1. Go to Certificates, IDs & Profiles > Identifiers
  2. Select the AppID you want to enable Broadcast Capability
  3. Enable Broadcast Capability under Push Notifications and save.
enable broadcast

Step2: Create a channel ​

You can maintain up to 10,000 channels for your app in the development and production environment, respectively.

You can use one of the following ways to create a channel:

  1. Use Apple's Apple Push Notification Console.
  2. Manually request channel management request API following Apple's instruction.
  3. Use my own APNs Channels tools which will request channel management request API.

WARNING

When I request Apple's channel management API with a bundleID that contains capital letters, I always receive a "TopicMismatch" error. I'm unsure why this is happening, as Apple's own Push Notification Console doesn't have this issue.

You can find the details of my request here.

Here are the steps to create a channel using my APNs Channels tool.

  1. Select "Authenticate using tokens" and provide the P8 key file, Key ID, Team ID.
  2. Select the "Environment" and enter the Bundle ID, excluding the ".push-type.liveactivity" suffix.
  3. Click the "+ New Channel" button.
  4. In the popup window, select the "Message Storage Policy".
  5. Then, click the "Create Channel" button.
  6. Then, go back to the main page, you will find the new created channel information in the list below.
    The ChannelID column is all you need.

Step3: Start a channel-subscribed Live Activity by code ​

In your app, you can manually start a Live Activity by calling the request(attributes:content:pushType:) function and pass channel with the channel ID as the pushType parameter.

swift
func startLiveActivityWithChannel(string channelId, initialState) {
    let activity = try Activity.request(
            attributes: adventure,
            content: .init(state: initialState, staleDate: nil),
            //Input your unique channel ID
            pushType: .channel(channelId)
}

Step4: Start a channel-subscribed Live Activity using push notifications ​

You can also start a channel-subscribed Live Activity by adding input-push-channel field to the payload of regular push-to-start Live Activity push notificaitons.

Host ​

Use HTTP/2 and TLS 1.2 or later to establish a connection between your provider server and one of the following servers.

  • Development/Sandbox Environment: api.sandbox.push.apple.com:443
  • Production Environment: api.push.apple.com:443

Request Header ​

  • :method: POST
  • :path: /3/device/<push_to_start_token>
  • authorization: bearer <provider_token>
  • apns-push-type: liveactivity
  • apns-topic: <your bundleID>.push-type.liveactivity
  • apns-priority: 5 or 10

Payload ​

  • timestamp: Current UNIX timestamp in seconds.
  • event: start
  • input-push-channel: <Channel ID>.
  • attributes-type: Your custom ActivityAttributes type. LiveActivityAttributes in my case.
  • attributes: Static data of your live activity content.
  • content-state: Dynamic data of your live activity content.
  • alert: Alert the user about a new Live Activity.
json
{
    "aps": {
        "timestamp": 1705547770,
        "event": "start",
        "input-push-channel": "CTrNsYq/Ee8AALLzHQaVlA==", 
        "content-state": {
            "emoji": "🍏🍏"
        },
        "attributes-type": "LiveActivityAttributes",
        "attributes": {
            "name": "Apple"
        },
        "alert": {
            "title": "Hello",
            "body": "World",
            "sound": "chime.aiff"
        }
    }
}

Step4: Update a channel-subscribed Live Activity With Broadcast Push Notifications ​

Then, you can update the Live Activity by sending update push notifications to the channel ID.

Host ​

Use HTTP/2 and TLS 1.2 or later to establish a connection between your provider server and one of the following servers.

  • Development/Sandbox Environment: api.sandbox.push.apple.com:443
  • Production Environment: api.push.apple.com:443

Request Header ​

  • :method: POST
  • :path: /4/broadcasts/apps/<your bundleID> (bundle ID excluding the .push-type.liveactivity suffix)
  • authorization: bearer <provider_token>
  • apns-push-type: liveactivity
  • apns-priority: 5 or 10
  • apns-channel-id: <Channel ID>
  • apns-expiration: UNIX timestamp in seconds represents the notification expiration time. If the channel's storage policy is No Message Stored, this value must not be zero.

Payload ​

  • timestamp: Current UNIX timestamp in seconds.
  • event: update
  • content-state: The latest dynamic data of your live activity content.
  • stale-date(optional): UNIX timestamp in seconds represents the time when the system will consider the Live Activity to be stale.
json
{
    "aps": {
        "timestamp": 1705560370,
        "event": "update",
        "content-state": {
            "emoji": "🍏🍑"
        },
        "stale-date": 1705567570
    }
}

Step5: End a channel-subscribed Live Activity With Broadcast Push Notifications ​

You can also end the Live Activity by sending a end push notification to the channel ID.

Host ​

Use HTTP/2 and TLS 1.2 or later to establish a connection between your provider server and one of the following servers.

  • Development/Sandbox Environment: api.sandbox.push.apple.com:443
  • Production Environment: api.push.apple.com:443

Request Header ​

  • apns-push-type: liveactivity
  • :path: /4/broadcasts/apps/<your bundleID> (bundle ID excluding the .push-type.liveactivity suffix)
  • apns-priority: 5 or 10
  • apns-channel-id: <Channel ID>
  • apns-expiration: UNIX timestamp in seconds represents the notification expiration time. If the channel's storage policy is No Message Stored, this value must not be zero.

Payload ​

  • timestamp: Current UNIX timestamp in seconds.
  • event: end
  • content-state: The final dynamic data of your live activity content.
  • dismissal-date:
    • The UNIX timestamp when the system will remove the Live Activity from the Lock Screen after it ends.
    • By default, It's four hours after the live activity ends.
    • If the value is in the past, the Live Activity will immediately dismiss after it ends.
json
{
    "aps": {
        "timestamp": 1705560370,
        "event": "end",
        "content-state": {
            "emoji": "🍑🍑"
        },
        "dismissal-date": 1705567570
    }
}

References ​