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Flagsmith Android/Kotlin SDK

This SDK can be used for Android applications written in Kotlin. The source code for the client is available on GitHub.

Installation​

Gradle​

repositories {
    google()
    mavenCentral()
}

In your project path app/build.gradle add a new dependency:

implementation("com.flagsmith:flagsmith-kotlin-android-client:1.7.2")

Basic Usage​

The SDK is initialised against a single environment within a project on https://flagsmith.com, for example the Development or Production environment. You can find your Client-side Environment Key in the Environment settings page.

Initialization​

Within your Activity inside onCreate()​

lateinit var flagsmith : Flagsmith

override fun onCreate(savedInstanceState: Bundle?) {
    initFlagsmith();
}

private fun initFlagsmith() {
    flagsmith = Flagsmith(environmentKey = FlagsmithConfigHelper.environmentDevelopmentKey, context = context)
}

Custom configuration​

The Flagsmith SDK has various parameters for initialisation. Most of these are optional, and allow you to configure the Flagsmith SDK to your specific needs:

  • environmentKey Take this API key from the Flagsmith dashboard and pass here
  • baseUrl By default we'll connect to the Flagsmith backend, but if you self-host you can configure here
  • context The current Context is required to use the Flagsmith Analytics functionality
  • enableAnalytics Enable analytics - default true. Disable this if you'd like to avoid the use of Context
  • analyticsFlushPeriod The period in seconds between attempts by the Flagsmith SDK to push analytic events to the server
  • enableRealtimeUpdates Enable the SDK to receive updates to features in real time while the app is running
  • defaultFlags Provide default flags the the SDK to ensure values are availble when no network connection can be made
  • cacheConfig Disabled by default, but when enabled will allow Flagsmith to fall back to cached values when no network connection can be made
  • request / read / writeTimeoutSeconds Fine-grained control of the HTTP timeouts used inside the Flagsmith SDK

Flags​

Now you are all set to retrieve feature flags from your project. To list and print all flags:

flagsmith.getFeatureFlags { result ->
    result.fold(
        onSuccess = { flagList ->
            Log.i("Flagsmith", "Current flags:")
            flagList.forEach { Log.i("Flagsmith", "- ${it.feature.name} - enabled: ${it.enabled} value: ${it.featureStateValue ?: "not set"}") }
        },
        onFailure = { err ->
            Log.e("Flagsmith", "Error getting feature flags", err)
        })
}

Get Flags for an identity​

To get feature flags for a specific identity:

flagsmith.getFeatureFlags(identity = "test-user@gmail.com") { result ->
    result.fold(
        onSuccess = { flagList ->
            Log.i("Flagsmith", "Current flags:")
            flagList.forEach { Log.i("Flagsmith", "- ${it.feature.name} - enabled: ${it.enabled} value: ${it.featureStateValue ?: "not set"}") }
        },
        onFailure = { err ->
            Log.e("Flagsmith", "Error getting feature flags", err)
        })
}

You can also get flags for an identity and set the traits at the same time:

flagsmith.getFeatureFlags(identity = "test-user@gmail.com", traits = listOf(Trait(key = "set-from-client", value = "12345"))) { result ->
    result.fold(
        onSuccess = { flagList ->
            Log.i("Flagsmith", "Current flags:")
            flagList.forEach { Log.i("Flagsmith", "- ${it.feature.name} - enabled: ${it.enabled} value: ${it.featureStateValue ?: "not set"}") }
        },
        onFailure = { err ->
            Log.e("Flagsmith", "Error getting feature flags", err)
        })
}

Get Flag Object by featureId​

To retrieve a feature flag boolean value by its name:

flagsmith.hasFeatureFlag(forFeatureId = "test_feature1") { result ->
    val isEnabled = result.getOrDefault(true)
    Log.i("Flagsmith", "test_feature1 is enabled? $isEnabled")
}

Create a Trait for a user identity​

flagsmith.setTrait(Trait(key = "set-from-client", value = "12345"), identity = "test@test.com") { result ->
    result.fold(
        onSuccess = { _ ->
            Log.i("Flagsmith", "Successfully set trait")

        },
        onFailure = { err ->
            Log.e("Flagsmith", "Error setting trait", err)
        })
}

Get all Traits​

To retrieve a trait for a particular identity as explained here Traits

flagsmith.getTraits(identity = "test@test.com") { result ->
    result.fold(
        onSuccess = { traits ->
            traits.forEach {
                Log.i("Flagsmith", "Trait - ${it.key} : ${it.traitValue}")
            }
        },
        onFailure = { err ->
            Log.e("Flagsmith", "Error getting traits", err)
        })
}

Providing Default Flags​

You can define default flag values when initialising the SDK. This ensures that your application works as intended in the event that it cannot receive a response from our API.

val defaultFlags = listOf(
    Flag(
        feature = Feature(
            id = 345345L,
            name = "Flag 1",
            createdDate = "2023‐07‐07T09:07:16Z",
            description = "Flag 1 description",
            type = "CONFIG",
            defaultEnabled = true,
            initialValue = "true"
        ), enabled = true, featureStateValue = "value1"
    ),
    Flag(
        feature = Feature(
            id = 34345L,
            name = "Flag 2",
            createdDate = "2023‐07‐07T09:07:16Z",
            description = "Flag 2 description",
            type = "CONFIG",
            defaultEnabled = true,
            initialValue = "true"
        ), enabled = true, featureStateValue = "value2"
    ),
)

// Then pass these during initialisation:
flagsmith = Flagsmith(
    environmentKey = FlagsmithConfigHelper  environmentDevelopmentKey,
    defaultFlags = defaultFlags,
    context = context)

Cache​

By default, the cache is off. When turned on, Flagsmith will cache all flags returned by the API (to permanent storage), and in case of a failed response, fall back on the cached values. The cache can be turned off or on during initialisation:

flagsmith = Flagsmith(
    environmentKey = FlagsmithConfigHelper  environmentDevelopmentKey,
    cacheConfig = FlagsmithCacheConfig(enableCache = true)
    context = context)

You can also set a TTL for the cache (in seconds) for finer control:

FlagsmithCacheConfig (
    enableCache = true,
    cacheTTLSeconds = 3600L, // 1 hour
    val cacheSize = 1024L * 1024L, // 1 MB
)

Override the default base URL​

By default, the client uses a default configuration. You can override the configuration as follows. If you're also using realtime flag updates in your hosted environment you'll also need to pass the eventSourceUrl in a similar fashion:

        flagsmith = Flagsmith(
            environmentKey = Helper.environmentDevelopmentKey,
            context = context,
            baseUrl = "https://hostedflagsmith.company.com/"),
            eventSourceUrl = "https://api.hostedflagsmith.company.com/"