Kotlin Specialist

# Android & Jetpack Compose

## Compose Basics

```kotlin
import androidx.compose.runtime.*
import androidx.compose.foundation.layout.*
import androidx.compose.material3.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp

@Composable
fun UserProfile(user: User, onEdit: () -> Unit) {
    Card(
        modifier = Modifier
            .fillMaxWidth()
            .padding(16.dp)
    ) {
        Column(modifier = Modifier.padding(16.dp)) {
            Text(
                text = user.name,
                style = MaterialTheme.typography.headlineMedium
            )
            Text(
                text = user.email,
                style = MaterialTheme.typography.bodyMedium,
                color = MaterialTheme.colorScheme.onSurfaceVariant
            )
            Spacer(modifier = Modifier.height(8.dp))
            Button(onClick = onEdit) {
                Text("Edit Profile")
            }
        }
    }
}
```

## State Management

```kotlin
// ViewModel with StateFlow
class UserViewModel(
    private val repository: UserRepository
) : ViewModel() {
    private val _uiState = MutableStateFlow(UserUiState())
    val uiState: StateFlow<UserUiState> = _uiState.asStateFlow()

    fun loadUser(userId: String) {
        viewModelScope.launch {
            _uiState.update { it.copy(isLoading = true) }
            try {
                val user = repository.getUser(userId)
                _uiState.update { it.copy(user = user, isLoading = false) }
            } catch (e: Exception) {
                _uiState.update { it.copy(error = e.message, isLoading = false) }
            }
        }
    }
}

data class UserUiState(
    val user: User? = null,
    val isLoading: Boolean = false,
    val error: String? = null
)

// Composable using ViewModel
@Composable
fun UserScreen(
    viewModel: UserViewModel = hiltViewModel(),
    userId: String
) {
    val uiState by viewModel.uiState.collectAsStateWithLifecycle()

    LaunchedEffect(userId) {
        viewModel.loadUser(userId)
    }

    when {
        uiState.isLoading -> LoadingIndicator()
        uiState.error != null -> ErrorMessage(uiState.error!!)
        uiState.user != null -> UserProfile(uiState.user!!)
    }
}
```

## Material 3 Theme

```kotlin
@Composable
fun AppTheme(
    darkTheme: Boolean = isSystemInDarkTheme(),
    content: @Composable () -> Unit
) {
    val colorScheme = if (darkTheme) {
        darkColorScheme(
            primary = Purple80,
            secondary = PurpleGrey80,
            tertiary = Pink80
        )
    } else {
        lightColorScheme(
            primary = Purple40,
            secondary = PurpleGrey40,
            tertiary = Pink40
        )
    }

    MaterialTheme(
        colorScheme = colorScheme,
        typography = Typography,
        content = content
    )
}
```

## Navigation

```kotlin
import androidx.navigation.compose.*

@Composable
fun AppNavigation() {
    val navController = rememberNavController()

    NavHost(
        navController = navController,
        startDestination = "home"
    ) {
        composable("home") {
            HomeScreen(
                onNavigateToProfile = { userId ->
                    navController.navigate("profile/$userId")
                }
            )
        }

        composable(
            route = "profile/{userId}",
            arguments = listOf(navArgument("userId") { type = NavType.StringType })
        ) { backStackEntry ->
            val userId = backStackEntry.arguments?.getString("userId")
            ProfileScreen(
                userId = userId ?: "",
                onBack = { navController.popBackStack() }
            )
        }

        composable("settings") {
            SettingsScreen()
        }
    }
}
```

## LazyColumn (Lists)

```kotlin
@Composable
fun UserList(
    users: List<User>,
    onUserClick: (User) -> Unit
) {
    LazyColumn(
        modifier = Modifier.fillMaxSize(),
        contentPadding = PaddingValues(16.dp),
        verticalArran