Using the SDKs

This topic explains how to get started using the Ably Asset Tracking SDKs.

Supported platforms

There are two Asset Tracking SDKs, one for publishing and one for subscribing. The following platforms are supported:

• Android (Java and Kotlin) - publisher and subscriber SDK
• iOS (Objective-C and Swift) - publisher and subscriber SDK
• Web (JavaScript, with first class TypeScript support) - subscriber SDK

SDK repositories

The SDKs can be found in the following GitHub repositories:

• Android
• iOS
• JavaScript

Prerequisites

You need to have a suitable development environment installed, for example:

• Android - Android Studio or Gradle (requires Android SDK to be installed)
• iOS - Xcode
• JavaScript - any suitable environment of your choice

You also need to have suitable credentials for the various SDK components:

• ABLY_API_KEY - Your Ably API key
• MAPBOX_ACCESS_TOKEN - Mapbox public key
• MAPBOX_DOWNLOADS_TOKEN - Mapbox private key

On Android development systems you can set these values in your ~/.gradle/gradle.properties file.

Installing the SDK

You can find information on installing the Ably Asset Tracking SDKs in the following resources:

• Instructions for Android
• Instructions for iOS
• Instructions for JavaScript

Authentication

The client requires authentication in order to establish a connection with Ably. There are three methods that can be used:

1. Basic authentication
2. Token authentication
3. JWT authentication

Usually a client will use either token or JWT authentication, as basic authentication would require exposing the API keys on the client.

Examples of establishing a connection using the three methods are given in the following sections. While the examples shown are for either the Publishing or Subscribing SDK, you can use the same approach for both SDKs.

Basic Authentication

The following example demonstrates establishing a connection using basic authentication:

This method should not be used on a client however, as it exposes the API key.

You can read more about basic authentication in our documentation.

Token Authentication

The following example demonstrates establishing a connection using token authentication:

You can read more about token authentication in our documentation.

JWT Authentication

The following example demonstrates establishing a connection using JWT authentication:

You can read more about JWT authentication in our documentation.

Using the Publishing SDK

Common operations you need to carry out on the publisher include:

• Initialize the publisher.
• Start tracking an asset.
• Stop tracking an asset.
• Set the resolution constraints on an asset.

Initializing the Publisher

During initialization of the publisher various methods can be called to configure the Builder interface of the Publisher.

The required methods are:

The optional methods are:

Other publisher methods of note are:

Publisher properties of note:

In the following sections you will learn how to set up some resolution constraints and then start publishing.

The following code example creates some example resolution constraints:

The next step is to create a default resolution to be used:

Once these are created you can then initialize the publisher with the constraints and default resolution, and start the publisher:

Start tracking

You can start tracking an asset (a Trackable), by calling the track or add method of the publisher. A Trackable is composed of the following:

• trackingID: The tracking identifier for the asset.
• destination: A Destination object, which is a latitude and longitude.
• constraints: A set of resolution constraints.

The track method adds a Trackable object, and makes it the actively tracked object, meaning that the state of the active field will be updated to this object, if that wasn't already the case. If this object was already in this publisher's tracked set, then this method only serves to change the actively tracked object. Takes a trackable as a parameter, which is the object to be added to this publisher's tracked set, if it's not already there, and which will be made the actively tracked object.

The add method adds a Trackable object, but does not make it the actively tracked object, meaning that the state of the active field will not change. If this object was already in this publisher's tracked set then this method does nothing. Takes a trackable as a parameter, which is the object to be added to this publisher's tracked set, if it's not already there.

Both of these methods return a StateFlow that represents the TrackableState of the added Trackable.

The following code example demonstrates how to start tracking an asset:

Stop tracking

You can stop tracking a trackable (asset) that is registered with the publisher using the remove method, as shown in the following code:

Using the Subscribing SDK

Common operations you will need to carry out on the subscriber include:

• Initialize the subscriber.
• Listen for location updates sent from from the publisher.
• Listen for asset status updates sent from the publisher.
• Request a different resolution to be sent from the publisher.

Initializing the Subscriber

During initialization of the subscriber various methods can be called to configure the Subscriber.

The required methods are:

• connection: Called to provide Ably connection information, such as API keys, and any other configuration parameters as needed.
• trackingId: Sets the asset to be tracked, using the unique tracking identifier of the asset.

The optional methods are:

• resolution: Request a specific resolution of updates to be requested from the remote publisher.
• logHandler: Sets the log handler (experimental API).
• start: Creates a Subscriber and starts listening for location updates.

The following code example demonstrates initializing and starting the subscriber:

Subscribe to updates

You can subscribe to updates from the publisher, specifying a function that is called when each update is received. This is shown in the following example:

You can also subscribe to raw locations if these have been enabled in the publisher (see the rawLocations(true) builder method). Once the raw locations are enabled by the publisher, you can access them using the subscriber's rawLocations flow, just as you do with the regular locations flow. This feature is only ever used for debugging purposes, and should not be used in a production situation.

Subscribe to asset state changes

You can subscribe to asset state changes from the publisher, specifying a function that is called when each state change is received. This is shown in the following example:

Request a different resolution

The subscriber can always request a different resolution preference by calling the resolutionPreference method, passing in the required Resolution. This is shown in the following example:

Subscriber properties that are useful include:

• resolutions: The shared flow emitting the publisher's resolution values when they become available.
• nextLocationUpdateIntervals: The shared flow emitting the estimated next location update intervals in milliseconds when they become available.

To observe the actual resolution, as opposed to the requested resolution:

See also the SDK reference docs for more Subscriber properties.

Location animator

The location animator is an extension for the subscriber that provides smooth location updates animation.

The location animator creates animation steps from location updates that are provided by the Subscriber SDK. These steps are then applied to an ongoing animation.

The animation duration is then recalculated as the sum of location update interval (the time to next location update from the publisher) and the intentional delay. The intentional delay allows for network issues or delays in the location updates. For example, if the intentional delay was set to two seconds, then a two second buffer will help the animation remain smooth and continuous, even if the publisher did not send a location update within the specified time, with a two second margin.

The location animator then recalculates each step duration to evenly take up the animation duration, so the overall animation of the trackable is smooth.

Each step is animated at 60 FPS, and this applies to the map marker.

More information can also be found in the location animator reference docs.

For the smooth location animation mechanism a flow is exposed:

Create an instance

Creating an instance of the location animator:

There are two optional parameters:

• intentionalAnimationDelayInMilliseconds: The higher the delay, the more buffer there is to allow for unexpected delays of location updates from the publisher. Also moves the actual position of the trackable backwards in time. The higher the setting the more network issues and delays are allowed for, but the position updates will be less realtime in nature. By default this is set to two seconds, but you should test what value works best for your use case.
• animationStepsBetweenCameraUpdates: By default, when a step is being animated, the camera position is also updated. But this can be changed so that the camera position updates, for example, on every five location updates.

Stop the location animator

As with other components, you can stop the location animator with the stop method:

The location animator should be stopped when no longer used to conserve resources.

Observing the animated positions

The location animator exposes a positions flow:

This provides data you can use to move your map marker on the map, or when you want to move your trackable in the screen. This flow is updated at 60 FPS when the animation is ongoing.

A camera positions flow is also provided:

This provides data you can use to move your camera whenever a new camera position is read.

Providing location updates to animate

To use the animator you need to provide it with some information:

• locationUpdate: The location update from the subscriber.
• expectedIntervalBetweenLocationUpdatesInMilliseconds: Obtained from subscriber API, expected time within which the publisher is expected to send a location update.

See also

• Overview
• Using the example apps
• Asset Tracking Android training workshop project
• Ably Asset Tracking Android SDK Reference - generated from source code
• Ably Asset Tracking Swift SDK Reference - generated from source code