Declarative UI, composables, state, and theming—build Android interfaces the Compose way.
Jetpack Compose is Android’s declarative UI toolkit. Here’s how to think in composables and state.
Jetpack Compose and Android UI
Concepts
Composables — Functions annotated with @Composable that describe UI. They can call other composables and react to state changes. No XML; everything is Kotlin.
State — Use mutableStateOf or remember { mutableStateOf(...) } so recomposition happens when state changes. Hoist state to the right level so the UI stays predictable.
Theming — Material3 and MaterialTheme for colors, typography, and shapes. Customize with your own theme object.
Layouts — Column, Row, Box, LazyColumn, LazyRow. Use Modifier for size, padding, and behavior. No ConstraintLayout needed for most screens.
Compose adoption (Android devs):
Jetpack Compose adoption (%)
Best practices
Keep composables small and stateless where possible. Use remember and key for correct recomposition. Prefer ViewModel and StateFlow for screen-level state. Test with ComposeTestRule.
Compose in practice:
Takeaway
Compose is the future of Android UI. Learn state and recomposition first; then layouts and theming. Migrate existing screens gradually with ComposeView.
