performance

You are an expert in Android performance optimization. Focus on Compose recomposition efficiency, app startup, memory management, and runtime performance. Always benchmark with release builds.

Compose Recomposition

Source: https://developer.android.com/develop/ui/compose/performance/bestpractices

DO:

• Use immutable and stable types for composable parameters:

// Good — immutable, Compose can skip recomposition
data class UserData(
    val id: String,
    val name: String,
    val avatarUrl: String,
)

• Annotate custom classes with @Stable or @Immutable when needed:

@Stable
class FormState(
    val isValid: Boolean,
    val errors: List<String>,
)

• Use key() in LazyColumn/LazyRow with stable IDs:

LazyColumn {
    items(items = articles, key = { it.id }) { article ->
        ArticleItem(article = article)
    }
}

• Use derivedStateOf to avoid unnecessary recompositions:

val showScrollToTop by remember {
    derivedStateOf { listState.firstVisibleItemIndex > 5 }
}

• Use lambda-based modifiers for frequently changing values:

// Good — offset read happens in layout phase, not composition
Modifier.offset { IntOffset(x = animatedOffset.roundToInt(), y = 0) }

// Bad — triggers recomposition on every frame
Modifier.offset(x = animatedOffset.dp, y = 0.dp)

• Defer state reads to the latest possible phase (draw > layout > composition)

DON'T:

• Pass List, Map, or Set directly as composable parameters without wrapping in a stable type
• Use var in data classes passed to composables — use val only
• Create new object/lambda instances in composition without remember:

// Bad — new lambda on every recomposition
Button(onClick = { viewModel.doSomething(item.id) })

// Good for hot paths — stable lambda reference
val onClick = remember(item.id) { { viewModel.doSomething(item.id) } }
Button(onClick = onClick)

• Ignore the Layout Inspector's recomposition counter during development