EXAMPLE Android

# PostHog configuration
posthog.apiKey=your_posthog_project_token
posthog.host=https://us.i.posthog.com

android {
    defaultConfig {
        buildConfigField "String", "POSTHOG_PROJECT_TOKEN", "\"your_posthog_project_token\""
        buildConfigField "String", "POSTHOG_HOST", "\"https://us.i.posthog.com\""
    }
}

├── app/
│   ├── src/
│   │   ├── main/
│   │   │   ├── java/com/example/posthog/
│   │   │   │   ├── BurritoApplication.kt      # Application class with PostHog initialization
│   │   │   │   ├── MainActivity.kt           # Main activity
│   │   │   │   ├── ui/
│   │   │   │   │   ├── screens/
│   │   │   │   │   │   ├── LoginScreen.kt     # Login screen with user identification
│   │   │   │   │   │   ├── BurritoScreen.kt   # Demo feature screen with event tracking
│   │   │   │   │   │   └── ProfileScreen.kt   # User profile with error tracking demo
│   │   │   │   │   └── components/            # Reusable UI components
│   │   │   │   └── utils/
│   │   │   │       └── PostHogHelper.kt       # PostHog utility functions
│   │   │   ├── res/                           # Resources (layouts, strings, etc.)
│   │   │   └── AndroidManifest.xml            # App manifest
│   │   └── test/                              # Unit tests
│   └── build.gradle                           # App-level Gradle configuration
├── build.gradle                               # Project-level Gradle configuration
├── settings.gradle                            # Gradle settings
└── local.properties                           # Local configuration (gitignored)

class BurritoApplication : Application() {
    override fun onCreate() {
        super.onCreate()
        
        val posthogConfig = PostHogConfig(
            apiKey = BuildConfig.POSTHOG_PROJECT_TOKEN,
            host = BuildConfig.POSTHOG_HOST
        ).apply {
            // Enable session replay
            sessionReplay = true
            
            // Enable automatic exception capture
            captureApplicationLifecycleEvents = true
            captureDeepLinks = true
            captureScreenViews = true
        }
        
        PostHog.setup(this, posthogConfig)
    }
}

val posthog = PostHog.getInstance()

fun handleLogin(username: String, password: String) {
    // Authenticate user
    val success = authenticateUser(username, password)
    
    if (success) {
        // Identify the user once on login/sign up
        posthog.identify(
            distinctId = username,
            properties = mapOf(
                "username" to username,
                "login_method" to "password"
            )
        )
        
        // Capture login event
        posthog.capture("user_logged_in", mapOf(
            "username" to username
        ))
    }
}

val posthog = PostHog.getInstance()

fun handleBurritoConsideration() {
    // Track custom event
    posthog.capture("burrito_considered", mapOf(
        "total_considerations" to considerationCount,
        "username" to currentUser.username,
        "timestamp" to System.currentTimeMillis()
    ))
    
    // Update user properties
    posthog.setUserProperties(mapOf(
        "last_burrito_consideration" to System.currentTimeMillis(),
        "total_burrito_considerations" to considerationCount
    ))
}

val posthogConfig = PostHogConfig(
    apiKey = BuildConfig.POSTHOG_PROJECT_TOKEN,
    host = BuildConfig.POSTHOG_HOST
).apply {
    // Automatic exception capture is enabled by default
    captureApplicationLifecycleEvents = true
}

val posthog = PostHog.getInstance()

try {
    // Risky operation
    performRiskyOperation()
} catch (e: Exception) {
    // Capture exception manually
    posthog.captureException(e, mapOf(
        "context" to "burrito_consideration",
        "user_id" to currentUser.id
    ))
}

val posthog = PostHog.getInstance()

// Manual screen view tracking
posthog.screen("BurritoScreen", mapOf(
    "screen_category" to "features",
    "user_type" to "premium"
))

val posthogConfig = PostHogConfig(
    apiKey = BuildConfig.POSTHOG_PROJECT_TOKEN,
    host = BuildConfig.POSTHOG_HOST
).apply {
    sessionReplay = true
    sessionReplayConfig = SessionReplayConfig(
        maskAllInputs = false, // Set to true to mask all input fields
        maskAllText = false    // Set to true to mask all text
    )
}

val posthog = PostHog.getInstance()
posthog.capture("event_name", mapOf("property" to "value"))

android {
    defaultConfig {
        // PostHog configuration
        buildConfigField "String", "POSTHOG_PROJECT_TOKEN", "\"${project.findProperty("posthog.apiKey") ?: ""}\""
        buildConfigField "String", "POSTHOG_HOST", "\"${project.findProperty("posthog.host") ?: "https://us.i.posthog.com"}\""
    }
}

dependencies {
    // PostHog Android SDK
    implementation 'com.posthog:posthog-android:3.+'
    
    // Other dependencies...
}

def localProperties = new Properties()
localProperties.load(new FileInputStream(rootProject.file("local.properties")))

android {
    defaultConfig {
        buildConfigField "String", "POSTHOG_PROJECT_TOKEN", "\"${localProperties.getProperty("posthog.apiKey", "")}\""
        buildConfigField "String", "POSTHOG_HOST", "\"${localProperties.getProperty("posthog.host", "https://us.i.posthog.com")}\""
    }
}

package com.example.posthog

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

class BurritoApplication : Application() {
    override fun onCreate() {
        super.onCreate()
        
        // Initialize PostHog early in Application lifecycle
        val config = PostHogAndroidConfig(
            apiKey = BuildConfig.POSTHOG_PROJECT_TOKEN,
            host = BuildConfig.POSTHOG_HOST,
        ).apply {
            debug = true
            errorTrackingConfig.autoCapture = true
        }
        
        PostHogAndroid.setup(this, config)
    }
}

package com.example.posthog.data

data class User(
    val username: String,
    val burritoConsiderations: Int = 0
)

package com.example.posthog.data

import android.content.Context
import android.content.SharedPreferences
import org.json.JSONObject

class UserRepository(context: Context) {

    private val prefs: SharedPreferences = context.getSharedPreferences(
        PREFS_NAME, Context.MODE_PRIVATE
    )

    companion object {
        private const val PREFS_NAME = "burrito_app_prefs"
        private const val KEY_CURRENT_USERNAME = "current_username"
        private const val KEY_USER_DATA_PREFIX = "user_data_"
    }

    fun getCurrentUsername(): String? {
        return prefs.getString(KEY_CURRENT_USERNAME, null)
    }

    fun getUser(username: String): User? {
        val json = prefs.getString("$KEY_USER_DATA_PREFIX$username", null) ?: return null
        return try {
            val obj = JSONObject(json)
            User(
                username = obj.getString("username"),
                burritoConsiderations = obj.getInt("burritoConsiderations")
            )
        } catch (e: Exception) {
            null
        }
    }

    fun saveUser(user: User) {
        val json = JSONObject().apply {
            put("username", user.username)
            put("burritoConsiderations", user.burritoConsiderations)
        }.toString()

        prefs.edit()
            .putString("$KEY_USER_DATA_PREFIX${user.username}", json)
            .putString(KEY_CURRENT_USERNAME, user.username)
            .apply()
    }

    fun clearCurrentUser() {
        prefs.edit()
            .remove(KEY_CURRENT_USERNAME)
            .apply()
    }

    fun getCurrentUser(): User? {
        val username = getCurrentUsername() ?: return null
        return getUser(username)
    }
}

package com.example.posthog

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.padding
import androidx.compose.material3.Scaffold
import androidx.compose.runtime.Composable
import androidx.compose.runtime.collectAsState
import androidx.compose.runtime.getValue
import androidx.compose.ui.Modifier
import androidx.lifecycle.viewmodel.compose.viewModel

package com.example.posthog.navigation

import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.collectAsState
import androidx.compose.runtime.getValue
import androidx.navigation.NavHostController
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
import com.example.posthog.ui.screens.BurritoScreen
import com.example.posthog.ui.screens.HomeScreen
import com.example.posthog.ui.screens.ProfileScreen
import com.example.posthog.viewmodel.AuthViewModel

sealed class Screen(val route: String) {
    object Home : Screen("home")
    object Burrito : Screen("burrito")
    object Profile : Screen("profile")
}

@Composable
fun NavGraph(
    navController: NavHostController,
    viewModel: AuthViewModel
) {
    val isAuthenticated by viewModel.isAuthenticated.collectAsState()
    val currentUser by viewModel.currentUser.collectAsState()

    NavHost(
        navController = navController,
        startDestination = Screen.Home.route
    ) {
        composable(Screen.Home.route) {
            HomeScreen(
                isAuthenticated = isAuthenticated,
                username = currentUser?.username,
                onLogin = { username -> viewModel.login(username) }
            )
        }

        composable(Screen.Burrito.route) {
            if (!isAuthenticated) {
                LaunchedEffect(Unit) {
                    navController.navigate(Screen.Home.route) {
                        popUpTo(Screen.Home.route) { inclusive = true }
                    }
                }
            } else {
                BurritoScreen(
                    burritoCount = currentUser?.burritoConsiderations ?: 0,
                    onConsiderBurrito = { viewModel.incrementBurritoCount() }
                )
            }
        }

        composable(Screen.Profile.route) {
            if (!isAuthenticated) {
                LaunchedEffect(Unit) {
                    navController.navigate(Screen.Home.route) {
                        popUpTo(Screen.Home.route) { inclusive = true }
                    }
                }
            } else {
                ProfileScreen(
                    username = currentUser?.username ?: "",
                    burritoCount = currentUser?.burritoConsiderations ?: 0
                )
            }
        }
    }
}

package com.example.posthog.ui.components

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.PaddingValues
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.material3.Button
import androidx.compose.material3.ButtonDefaults
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import com.example.posthog.ui.theme.DarkHeader
import com.example.posthog.ui.theme.ErrorRed
import com.example.posthog.ui.theme.White

@Composable
fun AppHeader(
    isAuthenticated: Boolean,
    username: String?,
    currentRoute: String?,
    onNavigate: (String) -> Unit,
    onLogout: () -> Unit
) {
    Box(
        modifier = Modifier
            .fillMaxWidth()
            .background(DarkHeader)
            .padding(horizontal = 16.dp, vertical = 12.dp)
    ) {
        Row(
            modifier = Modifier.fillMaxWidth(),
            horizontalArrangement = Arrangement.SpaceBetween,
            verticalAlignment = Alignment.CenterVertically
        ) {
            // App title
            Text(
                text = "Burrito App",
                color = White,
                fontSize = 18.sp
            )

            // User section (right side)
            if (isAuthenticated && username != null) {
                Row(
                    horizontalArrangement = Arrangement.spacedBy(12.dp),
                    verticalAlignment = Alignment.CenterVertically
                ) {
                    Text(
                        text = username,
                        color = White,
                        fontSize = 14.sp
                    )

                    Button(
                        onClick = onLogout,
                        colors = ButtonDefaults.buttonColors(
                            containerColor = ErrorRed
                        ),
                        shape = RoundedCornerShape(4.dp),
                        contentPadding = PaddingValues(horizontal = 12.dp, vertical = 6.dp)
                    ) {
                        Text(
                            text = "Logout",
                            color = White,
                            fontSize = 14.sp
                        )
                    }
                }
            }
        }
    }
}

package com.example.posthog.ui.components

import androidx.compose.foundation.layout.size
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Home
import androidx.compose.material.icons.filled.Person
import androidx.compose.material.icons.outlined.Home
import androidx.compose.material.icons.outlined.Person
import androidx.compose.material3.Icon
import androidx.compose.material3.NavigationBar
import androidx.compose.material3.NavigationBarItem
import androidx.compose.material3.NavigationBarItemDefaults
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import

package com.example.posthog.ui.components

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import com.example.posthog.ui.theme.LightGray
import com.example.posthog.ui.theme.TextDark
import com.example.posthog.ui.theme.TextGray

@Composable
fun StatsCard(
    title: String,
    value: String,
    modifier: Modifier = Modifier
) {
    Column(
        modifier = modifier
            .fillMaxWidth()
            .background(
                color = LightGray,
                shape = RoundedCornerShape(4.dp)
            )
            .padding(16.dp)
    ) {
        Text(
            text = title,
            color = TextGray,
            fontSize = 14.sp
        )
        Spacer(modifier = Modifier.height(4.dp))
        Text(
            text = value,
            color = TextDark,
            fontSize = 24.sp,
            fontWeight = FontWeight.Bold
        )
    }
}

package com.example.posthog.ui.screens

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.widthIn
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.foundation.verticalScroll
import androidx.compose.material3.Button

package com.example.posthog.ui.screens

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.widthIn
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.foundation.text.KeyboardOptions

package com.example.posthog.ui.screens

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.widthIn
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.foundation.verticalScroll
import androidx.compose.material3.Text

package com.example.posthog.ui.theme

import androidx.compose.ui.graphics.Color

val PrimaryBlue = Color(0xFF0070F3)
val PrimaryBlueHover = Color(0xFF0051CC)
val SuccessGreen = Color(0xFF28A745)
val SuccessGreenHover = Color(0xFF218838)
val ErrorRed = Color(0xFFDC3545)
val ErrorRedHover = Color(0xFFC82333)
val DarkHeader = Color(0xFF333333)
val DarkHeaderHover = Color(0xFF555555)
val LightGray = Color(0xFFF8F9FA)
val BorderGray = Color(0xFFDDDDDD)
val TextGray = Color(0xFF666666)
val BackgroundGray = Color(0xFFF5F5F5)
val TextDark = Color(0xFF333333)
val White = Color(0xFFFFFFFF)

package com.example.posthog.ui.theme

import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.lightColorScheme
import androidx.compose.runtime.Composable

private val LightColorScheme = lightColorScheme(
    primary = PrimaryBlue,
    secondary = SuccessGreen,
    tertiary = DarkHeader,
    background = BackgroundGray,
    surface = White,
    onPrimary = White,
    onSecondary = White,
    onTertiary = White,
    onBackground = TextDark,
    onSurface = TextDark
)

@Composable
fun PostHogTheme(
    content: @Composable () -> Unit
) {
    MaterialTheme(
        colorScheme = LightColorScheme,
        typography = Typography,
        content = content
    )
}

package com.example.posthog.ui.theme

import androidx.compose.material3.Typography
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.unit.sp

// Typography based on design specification
// Uses system font stack (FontFamily.Default maps to Roboto on Android)
val Typography = Typography(
    // H1 - Page titles (32sp)
    displayLarge = TextStyle(
        fontFamily = FontFamily.Default,
        fontWeight = FontWeight.SemiBold,
        fontSize = 32.sp,
        lineHeight = 40.sp,
        letterSpacing = 0.sp
    ),
    // H2 - Section titles (24sp)
    displayMedium = TextStyle(
        fontFamily = FontFamily.Default,
        fontWeight = FontWeight.SemiBold,
        fontSize = 24.sp,
        lineHeight = 32.sp,
        letterSpacing = 0.sp
    ),
    // H3 - Subsection titles (20sp)
    displaySmall = TextStyle(
        fontFamily = FontFamily.Default,
        fontWeight = FontWeight.SemiBold,
        fontSize = 20.sp,
        lineHeight = 26.sp,
        letterSpacing = 0.sp
    ),
    // Body text (16sp with 1.6 line height = 25.6sp)
    bodyLarge = TextStyle(
        fontFamily = FontFamily.Default,
        fontWeight = FontWeight.Normal,
        fontSize = 16.sp,
        lineHeight = 26.sp,
        letterSpacing = 0.sp
    ),
    // Small/Note text (14sp)
    bodySmall = TextStyle(
        fontFamily = FontFamily.Default,
        fontWeight = FontWeight.Normal,
        fontSize = 14.sp,
        lineHeight = 21.sp,
        letterSpacing = 0.sp
    ),
    // Labels (16sp, medium weight)
    labelLarge = TextStyle(
        fontFamily = FontFamily.Default,
        fontWeight = FontWeight.Medium,
        fontSize = 16.sp,
        lineHeight = 24.sp,
        letterSpacing = 0.sp
    ),
    // Button text - Burrito button (18sp)
    titleLarge = TextStyle(
        fontFamily = FontFamily.Default,
        fontWeight = FontWeight.Normal,
        fontSize = 18.sp,
        lineHeight = 24.sp,
        letterSpacing = 0.sp
    ),
    // Button text - Primary/Logout (16sp/14sp)
    titleMedium = TextStyle(
        fontFamily = FontFamily.Default,
        fontWeight = FontWeight.Normal,
        fontSize = 16.sp,
        lineHeight = 24.sp,
        letterSpacing = 0.sp
    ),
    titleSmall = TextStyle(
        fontFamily = FontFamily.Default,
        fontWeight = FontWeight.Normal,
        fontSize = 14.sp,
        lineHeight = 20.sp,
        letterSpacing = 0.sp
    )
)

package com.example.posthog.viewmodel

import android.app.Application
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.viewModelScope
import com.example.posthog.data.User
import com.example.posthog.data.UserRepository
import com.posthog.PostHog
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.asStateFlow
import kotlinx.coroutines.launch

class AuthViewModel(application: Application) : AndroidViewModel(application) {

    private val repository = UserRepository(application)

    private val _currentUser = MutableStateFlow<User?>(null)
    val currentUser: StateFlow<User?> = _currentUser.asStateFlow()

    private val _isAuthenticated = MutableStateFlow(false)
    val isAuthenticated: StateFlow<Boolean> = _isAuthenticated.asStateFlow()

    init {
        loadCurrentUser()
    }

    private fun loadCurrentUser() {
        viewModelScope.launch {
            val user = repository.getCurrentUser()
            _currentUser.value = user
            _isAuthenticated.value = user != null
        }
    }

    fun login(username: String) {
        viewModelScope.launch {
            val existingUser = repository.getUser(username)
            val user = existingUser ?: User(username = username, burritoConsiderations = 0)
            repository.saveUser(user)
            _currentUser.value = user
            _isAuthenticated.value = true

            PostHog.identify(username)
            PostHog.capture(event = "user_logged_in")
        }
    }

    fun logout() {
        viewModelScope.launch {
            PostHog.capture("user_logged_out")
            PostHog.reset()
            repository.clearCurrentUser()
            _currentUser.value = null
            _isAuthenticated.value = false
        }
    }

    fun incrementBurritoCount() {
        viewModelScope.launch {
            val user = _currentUser.value ?: return@launch
            val updatedUser = user.copy(burritoConsiderations = user.burritoConsiderations + 1)
            repository.saveUser(updatedUser)
            _currentUser.value = updatedUser

            PostHog.capture(
                event = "burrito_considered",
                properties = mapOf(
                    "total_considerations" to updatedUser.burritoConsiderations,
                    "username" to updatedUser.username
                )
            )
        }
    }
}