Android Jetpack Compose Guide

Applies to: Android SDK 24+, Jetpack Compose 1.5+, Kotlin 1.9+, Material Design 3

Core Principles

1. Declarative UI: Describe what the UI should look like, not how to build it step-by-step
2. Unidirectional Data Flow: State flows down, events flow up -- always
3. Composable Functions Are Cheap: The framework handles when to recompose; keep composables pure
4. State Hoisting: Lift state to the nearest common ancestor that needs it
5. Lifecycle Awareness: Collect flows with collectAsStateWithLifecycle(), never raw collectAsState()

Guardrails

Composable Conventions

• Every composable accepts modifier: Modifier = Modifier as its first optional parameter
• Keep composables small and focused (one responsibility per function)
• Use @Preview on every reusable component with representative data