Android On Device Evaluation SDK

Source code: statsig-io/android-local-eval

Statsig’s normal (remote evaluation) SDKs are recommended for most client applications. Understand the use case and privacy risks by reading the On-Device Eval SDK overview. On-device evaluation SDKs are for Enterprise & Pro Tier only.

These SDKs use a different paradigm than their precomputed counterparts: JS, Android, iOS, they behave more like Server SDKs. Rather than requiring a user up front, you can check gates/configs/experiments for any set of user properties, because the SDK downloads a complete representation of your project and evaluates checks in real time.

Pros

No need for a network request when changing user properties - just check the gate/config/experiment locally
Can bring your own CDN or synchronously initialize with a preloaded project definition
Lower latency to download configs cached at the edge, rather than evaluated for a given user (which cannot be cached as much)

Cons

Entire project definition is available client side - the names and configurations of all experiments and feature flags accessible by your client key are exposed. See our client key with server permission best practices
Payload size is strictly larger than what is required for the traditional SDKs
Evaluation performance is slightly slower - rather than looking up the value, the SDK must actually evaluate targeting conditions and an allocation decision
Does not support ID list segments with > 1000 IDs
Does not support IP or User Agent based checks (Browser Version/Name, OS Version/Name, IP, Country)

Set Up the SDK

Install the SDK

You can install the SDK using JitPack. See the latest version and installation steps at https://jitpack.io/#statsig-io/android-local-eval.

Initialize the SDK

Next, initialize the SDK with a client SDK key from the “API Keys” tab on the Statsig console. These keys are safe to embed in a client application.Along with the key, pass in a User Object with the attributes you’d like to target later on in a gate or experiment.

For On-Device Evaluation, you’ll need to add the “Allow Download Config Specs” scope. Client keys, by default, are not able to download the project definition for on-device evaluation.While client keys are safe to include, Server and Console keys should always be kept private.

How to add the scope

New SDK Keys
Existing SDK Keys

When creating a new client key, select “Allow Download Config Specs”

import com.statsig.androidlocalevalsdk.*;

// ...

android.app.Application app = // ref to your Application instance

StatsigOptions opts = new StatsigOptions();
opts.setEnvironmentParameter("tier", "staging");

StatsigClient client = Statsig.INSTANCE.getClient();
client.initializeAsync(
        app,
        "client-YOUR_CLIENT_SDK_KEY",
        new IStatsigCallback() {
            @Override
            public void onStatsigInitialize(@NotNull InitializationDetails initDetails) {
                // Statsig Ready
            }

            @Override
            public void onStatsigInitialize() {
                // deprecated
            }
        },
        opts
);

// or, create your own instance of StatsigClient
StatsigClient client = new StatsigClient();
client.initializeAsync(...);

Synchronous Initialization

import com.statsig.androidlocalevalsdk.*

 // (optional) Configure the SDK if needed
val opts = StatsigOptions()
opts.environment.tier = "staging"

val specs = "..." // JSON string of your configurations

let details = Statsig.client.initializeSync(application, "client-YOUR_CLIENT_SDK_KEY", specs, opts)

It is possible to configure the SDK to use cached values if they are newer than the local file. This can be useful if you ship your app with a local file, but would like it to only be used for the first session. In the following example, the SDK will only use initialSpecs if there is no cache or if the cache is older than initialSpecs.

val options = StatsigOptions()
options.useNewerCacheValuesOverProvidedValues = true

Statsig.client.initializeSync(
  application,
  "client-YOUR_CLIENT_SDK_KEY",
  specs,
  options
)

You can get a copy of your current specs data by visiting: https://api.statsigcdn.com/v1/download_config_specs/client-{YOUR_SDK_KEY}.json

Working with the SDK

Checking a Feature Flag/Gate

Now that your SDK is initialized, let’s check a Feature Gate. Feature Gates can be used to create logic branches in code that can be rolled out to different users from the Statsig Console. Gates are always CLOSED or OFF (think return false;) by default.

StatsigUser user = new StatsigUser("a-user");
StatsigClient client = Statsig.INSTANCE.getClient();

if (client.checkGate(user, "new_homepage_design")) {
  // Gate is on, show new home page
} else {
  // Gate is off, show old home page
}

Reading a Dynamic Config

Feature Gates can be very useful for simple on/off switches, with optional but advanced user targeting. However, if you want to be able send a different set of values (strings, numbers, and etc.) to your clients based on specific user attributes, e.g. country, Dynamic Configs can help you with that. The API is very similar to Feature Gates, but you get an entire json object you can configure on the server and you can fetch typed parameters from it. For example:

StatsigUser user = new StatsigUser("a-user");
StatsigClient client = Statsig.INSTANCE.getClient();

DynamicConfig config = client.getConfig(user, "awesome_product_details");

// The 2nd parameter is the default value to be used in case the given parameter name does not exist on
// the Dynamic Config object. This can happen when there is a typo, or when the user is offline and the
// value has not been cached on the client.
String itemName = config.getString("product_name", "Awesome Product v1");
Double price = config.getDouble("price", 10.0);
Boolean shouldDiscount = config.getBoolean("discount", false);

Getting a Layer/Experiment

Then we have Layers/Experiments, which you can use to run A/B/n experiments. We offer two APIs, but we recommend the use of layers to enable quicker iterations with parameter reuse.

StatsigUser user = new StatsigUser("a-user");
StatsigClient client = Statsig.INSTANCE.getClient();

// Values via getLayer
Layer layer = client.getLayer(user, "user_promo_experiments")
String promoTitle = layer.getString("title", "Welcome to Statsig!");
Double discount = layer.getDouble("discount", 0.1);

// or, via getExperiment
DynamicConfig titleExperiment = client.getExperiment(user, "new_user_promo_title");
DynamicConfig priceExperiment = client.getExperiment(user, "new_user_promo_price");

String promoTitle = titleExperiment.getString("title", "Welcome to Statsig!");
Double discount = priceExperiment.getDouble("discount", 0.1);

...

Double price = msrp * (1 - discount);

Logging an Event

Now that you have a Feature Gate or an Experiment set up, you may want to track some custom events and see how your new features or different experiment groups affect these events. This is super easy with Statsig - simply call the Log Event API for the event, and you can additionally provide some value and/or an object of metadata to be logged together with the event:

StatsigUser user = new StatsigUser("user_id");
StatsigClient client = Statsig.INSTANCE.getClient();

client.logEvent(user, "purchase", 2.99, Map.of("item_name", "remove_ads"));

Code Examples

Working sample apps are available in the repository:

Java & Kotlin Examples

Statsig User

You need to provide a StatsigUser object to check/get your configurations. You should pass as much information as possible in order to take advantage of advanced gate and config conditions. Most of the time, the userID field is needed in order to provide a consistent experience for a given user (see logged-out experiments to understand how to correctly run experiments for logged-out users). Besides userID, we also have email, ip, userAgent, country, locale and appVersion as top-level fields on StatsigUser. In addition, you can pass any key-value pairs in an object/dictionary to the custom field and be able to create targeting based on them. Once the user logs in or has an update/changed, make sure to call updateUser with the updated userID and/or any other updated user attributes:

For the Android On-Device Evaluation SDK, you pass the `StatsigUser` object directly into each evaluation method (`checkGate`, `getConfig`, etc.) rather than during initialization.

Unlike precomputed evaluation SDKs, the on-device evaluation SDK does not have an `updateUser` method since it evaluates gates/configs/experiments in real-time for any user object you pass in.

Setting a Global User

To avoid needing to pass the user object to every single evaluation call, you can set a global user. Then, when checking a gate/experiment/layer, provide “null” for the user to use the global user. This user will be used for all evaluations unless otherwise specified.

Statsig.client.setGlobalUser(myGlobalUser)

Statsig.client.checkGate(null, "my_gate") // <- Will use myGlobalUser
Statsig.client.checkGate(StatsigUser(userID: "user-123"), "my_gate") // <- Will NOT use myGlobalUser

Statsig Options

You can pass in an optional parameter options in addition to sdkKey and user during initialization to customize the Statsig client.

configSpecAPI

String

The endpoint to use for downloading config spec network requests. You should not need to override this (unless you have another API that implements the Statsig API endpoints).

eventLoggingAPI

String

default:"https://events.statsigapi.net/v1/rgstr"

The endpoint to use for log events. You should not need to override this (unless you have another API that implements the Statsig API endpoints).

initTimeoutMs

Long

default:"3000"

Milliseconds to wait for the initial network request before calling the completion block. The Statsig client will return either cached values (if any) or default values if checkGate/getConfig/getExperiment is called before the initial network request completes. Set to 0 to wait indefinitely for the latest values.

overrideStableID

String?

default:"null"

Overrides the stableID in the SDK that is set for the user.

loadCacheAsync

Boolean

default:"false"

Whether or not the SDK should block on loading saved values from disk.

initializeValues

Map<String, Any>?

default:"null"

Provide the download_config_specs response values directly to the Android SDK to synchronously initialize the client. You can get a copy of your current specs data by visiting: https://api.statsigcdn.com/v1/download_config_specs/client-{YOUR_SDK_KEY}.json

disableDiagnosticsLogging

Boolean

default:"false"

Prevent the SDK from sending useful debug information to Statsig.

Methods

setTier | setEnvironmentParameter | getEnvironment
- Used to signal the environment tier the user is currently in.
- setTier can be PRODUCTION, STAGING or DEVELOPMENT. e.g. passing in a value of Tier.STAGING will allow your users to pass any condition that pass for the staging environment tier, and fail any condition that only passes for other environment tiers.
- setEnvironmentParameter can be used for custom tiers, eg options.setEnvironmentParameter("tier", "test")

Lifecycle & Advanced Usage

Shutting Statsig Down

In order to save users’ data and battery usage, as well as prevent logged events from being dropped, we keep event logs in client cache and flush periodically. Because of this, some events may not have been sent when your app shuts down. To make sure all logged events are properly flushed or saved locally, you should tell Statsig to shutdown when your app is closing:

Statsig.shutdown();

Post Init Syncing

From Network

By default, the SDK will only sync during initialization. If you would like to re-sync after initialization, you can call the Statsig.client.updateAsync method. This will trigger a network call to fetch the latest changes from the server.

val details = Statsig.client.updateAsync()

Scheduled Polling

If you would like the SDK to regularly poll for updates, you can start the polling task with Statsig.client.scheduleBackgroundUpdates(). This will hit the network and pull down the latest changes.

val pollingTask = Statsig.cloent.scheduleBackgroundUpdates() // Defaults to 1 hour interval

// or, specify a custom interval
val intervalSeconds = 300
val pollingTask = Statsig.client.scheduleBackgroundUpdates(intervalSeconds)

// and, if you need to cancel it later
pollingTask?.cancel()

Using Persistent Evaluations

If you want to ensure that a user’s variant stays consistent while an experiment is running, regardless of changes to allocation or targeting, you can implement the UserPersistentStorageInterface and set it in StatsigOptions when you initialize the SDK.

Synchronous Persistent Evaluations

The UserPersistentStorageInterface exposes two methods for synchronous persistent storage, which will be called by default when evaluating an experiment.

interface UserPersistentStorageInterface {
    suspend fun load(key: String): PersistedValues
    fun save(key: String, experimentName: String, data: String)
    fun delete(key: String, experiment: String)
    ...
}

The key string is a combination of ID and ID Type: e.g. “123:userID” or “abc:stableID” which the SDK will construct and call get and set on by default You can use this interface to persist evaluations synchronously to local storage. If you need an async interface, read on.

Asynchronous Persistent Evaluations

The UserPersistentStorageInterface exposes two methods for asynchronous persistent evaluations. Because the getExperiment call is synchronous, you must load the value first, and pass it in as userPersistedValues

interface UserPersistentStorageInterface {
    fun loadAsync(key: String, callback: IPersistentStorageCallback)
    fun save(key: String, experimentName: String, data: String)
    fun delete(key: String, experiment: String)
    ...
}
interface IPersistentStorageCallback {
    fun onLoaded(values: PersistedValues)
}

For your convenience, we’ve created a top level method to load the value for a given user and ID Type:

// Asynchronous load values
val userPersistedValues = Statsig.client.loadUserPersistedValuesAsync(
  user: StatsigUser,
  idType: string, // userID, stableID, customIDxyz, etc
  callback: IPersistentStorageCallback
);

// Synchronous load values 
val userPersistedvalues = Statsig.client.loadUserPersistedValues(
    user: StatsigUser,
  idType: string, // userID, stableID, customIDxyz, etc
)

Putting it all together, assuming you have implemented the UserPersistentStorageInterface and set it on StatsigOptions, your call site will look like this:

// Asynchronous 
val callback = object: IPersistentStorageCallback {
    @override
    fun onLoaded(values: PersistedValues) {
        Statsig.getExperiment(user, "sample_experiment", GetExperimentOptions(userPersistedValues = values))
    }
}
val userValues = Statsig.client.loadUserPersistedValuesAsync(user, "userID", callback)

// Synchronous
val user = StatsigUser(userID = "user123")
val userValues = Statsig.client.loadUserPersistedValues(user, 'userID');
const experiment = statsig.getExperiment({userID: "123"}, 'the_allocated_experiment', { userPersistedValues: userValues });

If you are using java, you can only override loadAsync function and ignore load function as empty.

Local Overrides

It is possible to override the values returned by the Statsig SDK. This can be useful in unit testing or for enabling features for local development. To get setup with local overrides, you can pass an instance of LocalOverrideAdapter to the SDK via the StatsigOptions object.

It is possible to write your own override adapter. You can implement the IOverrideAdapter interface and pass that in instead.

val user = StatsigUser("user-a")

val overrides = LocalOverrideAdapter()

// Override a gate
overrides.setGate(user, "local_override_gate", true)

// Override a dynamic config (Similar for Layer and Experiment)
val config = DynamicConfig("local_override_dynamic_config", mapOf("key" to "val"))
overrides.setConfig(user, config)

val opts = StatsigOptions()
opts.overrideAdapter = overrides

Statsig.client.initializeAsync(
  app, 
  YOUR_SDK_KEY, 
  callback, 
  opts // <- Pass in StatsigOptions
)

FAQs

How do I run experiments for logged out users?

See the guide on device level experiments.

SDK Quickstarts

SDK Concepts

Client SDKs

Server SDKs

More SDK Methods

Console API Reference

Statsig CLI

HTTP API Reference

Pros

Cons

Set Up the SDK

Synchronous Initialization

Working with the SDK

Checking a Feature Flag/Gate

Reading a Dynamic Config

Getting a Layer/Experiment

Logging an Event

Code Examples

Statsig User

Setting a Global User

Statsig Options

Methods

Lifecycle & Advanced Usage

Shutting Statsig Down

Post Init Syncing

From Network

Scheduled Polling

Using Persistent Evaluations

Synchronous Persistent Evaluations

Asynchronous Persistent Evaluations

Local Overrides

FAQs

Additional Resources

SDK Quickstarts

SDK Concepts

Client SDKs

Server SDKs

More SDK Methods

Console API Reference

Statsig CLI

HTTP API Reference

​Pros

​Cons

​Set Up the SDK

​Synchronous Initialization

​Working with the SDK

​Checking a Feature Flag/Gate

​Reading a Dynamic Config

​Getting a Layer/Experiment

​Logging an Event

​Code Examples

​Statsig User

​Setting a Global User

​Statsig Options

​Methods

​Lifecycle & Advanced Usage

​Shutting Statsig Down

​Post Init Syncing

​From Network

​Scheduled Polling

​Using Persistent Evaluations

​Synchronous Persistent Evaluations

​Asynchronous Persistent Evaluations

​Local Overrides

​FAQs

​Additional Resources

Pros

Cons

Set Up the SDK

Synchronous Initialization

Working with the SDK

Checking a Feature Flag/Gate

Reading a Dynamic Config

Getting a Layer/Experiment

Logging an Event

Code Examples

Statsig User

Setting a Global User

Statsig Options

Methods

Lifecycle & Advanced Usage

Shutting Statsig Down

Post Init Syncing

From Network

Scheduled Polling

Using Persistent Evaluations

Synchronous Persistent Evaluations

Asynchronous Persistent Evaluations

Local Overrides

FAQs

Additional Resources