Android experiments installation

The best way to install the PostHog Android library is with a build system like Gradle. This ensures you can easily upgrade to the latest versions.

All you need to do is add the posthog-android module to your App's build.gradle or build.gradle.kts:

dependencies {
  implementation("com.posthog:posthog-android:3.+")
}

Configuration

The best place to initialize the client is in your Application subclass.

import android.app.Application
import com.posthog.android.PostHogAndroid
import com.posthog.android.PostHogAndroidConfig

class SampleApp : Application() {

    companion object {
        const val POSTHOG_API_KEY = "<ph_project_api_key>"
        // usually 'https://us.i.posthog.com' or 'https://eu.i.posthog.com'
        const val POSTHOG_HOST = "https://us.i.posthog.com"
    }

    override fun onCreate() {
        super.onCreate()

        val config = PostHogAndroidConfig(
            apiKey = POSTHOG_API_KEY,
            host = POSTHOG_HOST 
        )
        PostHogAndroid.setup(this, config)
    }
}

Once PostHog is initialized, you should be able to capture events. For your experiment to be meaningful, we need to capture an event that we want to measure, such as a conversion event.

For this tutorial, we can track a simple button click on a CTA as a conversion event.

// other imports
import com.posthog.PostHog

@Composable
fun SomeView() {
    Button(
        onClick = {
            PostHog.capture("cta clicked")
        }
    ) {
        Text("Call to action text")
    }
}

Before proceeding, let's make sure events are being captured and sent to PostHog. You should see cta clicked events appear in the Activity feed.

Go to the Experiments tab in the PostHog app and click on the New experiment button in the top right.

For this tutorial, let's create a new experiment using simplified test values:

• Name: "Test experiment"
• Description: "This is a test experiment"
• Feature flag key: "test-experiment-ff-key"
• Experiment type: "Feature flag"
• Variants: "control" and "test"
• Participant type: "Users"

Then click Save as draft.

Scroll down to the Primary metrics section and click + Add primary metric.

Choose Single-use and select Type > Mean.

Then search for the event cta clicked under Metric and click Save.

By default, experiments are exposed to 100% of users. You can customize release conditions to expose the experiment to a subset of users.

For this tutorial, we'll ship the experiment to all users and click Launch in the top right.

Use the PostHog SDK to call the experiment flag and update how your app renders based on the assigned variant.

// other imports
import com.posthog.PostHog

@Composable
fun SomeView() {
    if (PostHog.getFeatureFlag("experiment-feature-flag-key") == "test") {
        Button(
            onClick = {
                PostHog.capture("variant_button_clicked")
            }
        ) {
            Text("Variant Button")
        }
    } else {
        Button(
            onClick = {
                PostHog.capture("control_button_clicked")
            }
        ) {
            Text("Control Button")
        }
    }
}

Now when a user triggers a cta clicked event, PostHog automatically assigns the user to a variant and records an experiment exposure.

By default, users are split equally between variants. If you want to assign specific users to a specific variant, see more about distribution and release conditions.

Make sure exposures and feature flag calls are being sent to PostHog. You should see $feature_flag_called events appear in the Activity feed.

As you capture more cta clicked events, more exposures will populate the primary metrics in your experiment.

With enough data, you can analyze the experiment and its variants by:

• Conversion rates
• Statistical significance
• Credible intervals
• Chance to win %
• Minimum detectable effect
• And more