collecting-flows-safely

Collecting Flows Safely — keep upstream work tied to the UI lifecycle

collectAsState() keeps collecting whenever the composable is in composition, including while the app is backgrounded — that wastes CPU and battery. collectAsStateWithLifecycle() ties collection to a Lifecycle.State (default STARTED) so backgrounding pauses upstream work. For chatty flows, pair the consumer with .conflate() and .distinctUntilChanged() so Compose only sees meaningful changes. Skydoves hot take #4: a Flow<T> parameter on a composable is unstable and blocks skipping for the whole composable — collect at the caller and pass the resolved value.

When to use this skill

• A ViewModel or Repository exposes StateFlow<T>, SharedFlow<T>, or a cold Flow<T> to a Compose screen.
• The user reports background battery drain, "the screen keeps working when the app is in the recents tray", or wakelock noise on logcat.
• A composable consumes sensor data, location, GPS, websocket, or animation frames coming from outside Compose.
• A composable's signature is fun MyScreen(state: Flow<State>) (Flow-as-parameter antipattern).
• The user asks about collectAsState vs collectAsStateWithLifecycle, or about Lifecycle.State.STARTED / RESUMED semantics.
• The user wants Compose state to drive a non-Compose subscriber (analytics on visible item index, etc.) — that is the State→Flow direction served by snapshotFlow.

When NOT to use this skill

• The flow is constructed and consumed entirely inside one composable's remember { ... } block — that is composition-internal state, prefer mutableStateOf directly. See ../using-efficient-effects/SKILL.md for choosing the right effect API.
• The data source is already State<T> (e.g. mutableStateOf, Animatable.asState()) — do not wrap it in a flow just to call collectAsStateWithLifecycle().
• A truly always-on background listener that must run while the Activity is STOPPED. Move that work to a Service / WorkManager / repeatOnLifecycle in the Activity, not into Compose.