Android Performance

Android Performance

Compose Performance

Stability & Recomposition

// Mark classes as @Immutable when passed to Composable
@Immutable
data class ItemUiModel(val id: String, val name: String, val coverUrl: String)

// Lambda parameters are stable - prefer over direct ViewModel access
@Composable fun ItemCard(onItemClick: () -> Unit)           // GOOD: stable
@Composable fun ItemCard(viewModel: SampleViewModel)        // BAD: unstable

remember & derivedStateOf

val sortedItems = remember(items) { items.sortedBy { it.name } }  // cache expensive computation
val hasItems by remember { derivedStateOf { items.isNotEmpty() } }  // derived from other state

LazyList Performance

// Always provide stable keys
LazyColumn {
    items(items, key = { it.id }) { item -> ItemComponent(item) }
}

// contentType for heterogeneous lists
LazyColumn {
    items(items, key = { it.id }, contentType = { it.type }) { item ->
        when (item) {
            is Header -> HeaderComponent(item)
            is Item   -> ItemComponent(item)
        }
    }
}

Image Loading (Coil)

AsyncImage(
    model = ImageRequest.Builder(LocalContext.current)
        .data(item.imageUrl)
        .crossfade(true)
        .build(),
    contentDescription = item.name,
    modifier = Modifier.size(120.dp, 160.dp),
)

Paging Performance

// ALWAYS cachedIn(viewModelScope) to survive configuration changes
val result = callPagingDataWithInternet(
    callFlow = { useCase() },
    showErrorToast(it) },
).cachedIn(viewModelScope)  // Essential!

// PagingConfig tuning
PagingConfig(
    pageSize = 20,
    prefetchDistance = 5,         // How far ahead to prefetch
    enablePlaceholders = false,   // false for network-only
    initialLoadSize = 40,         // First page size
)

Memory Management

// WRONG: Context in ViewModel = memory leak
class MyViewModel(private val context: Context)

// RIGHT: ApplicationContext via Hilt
@HiltViewModel
class MyViewModel @Inject constructor(
    @ApplicationContext private val appContext: Context
) : BaseViewModel<...>()

// Collect flows lifecycle-aware
val state by viewModel.uiState.collectAsStateWithLifecycle()

Network Performance

OkHttpClient.Builder()
    .cache(Cache(cacheDir, 10 * 1024 * 1024))  // 10MB cache
    .connectTimeout(30, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build()

ProGuard/R8 Rules

# Moshi
-keep class com.template.data.**.dto.** { *; }
-keepclassmembers class * { @com.squareup.moshi.Json <fields>; }

# Konvert generated mappers
-keep class com.template.data.**.mapper.** { *; }