collecting-flows-safely

Name: collecting-flows-safely
Author: skydoves

454stars15forks

How to install collecting-flows-safely?

skydoves/compose-performance-skills/collecting-flows-safely

$npx -y skills add skydoves/compose-performance-skills --skill collecting-flows-safely

Installs into the current project.

Summary

Use this skill to migrate Compose UI from collectAsState() to collectAsStateWithLifecycle(), hoist Flow<T> parameters out of composables, and apply .conflate() / .distinctUntilChanged() / snapshotFlow so background CPU and battery stop draining and chatty flows stop i

Files · 1

View on GitHub

SKILL.md

1	# Collecting Flows Safely — keep upstream work tied to the UI lifecycle
2
3	`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.
4
5	## When to use this skill
6
7	- A `ViewModel` or `Repository` exposes `StateFlow<T>`, `SharedFlow<T>`, or a cold `Flow<T>` to a Compose screen.
8	- The user reports background battery drain, "the screen keeps working when the app is in the recents tray", or wakelock noise on logcat.
9	- A composable consumes sensor data, location, GPS, websocket, or animation frames coming from outside Compose.
10	- A composable's signature is `fun MyScreen(state: Flow<State>)` (Flow-as-parameter antipattern).
11	- The user asks about `collectAsState` vs `collectAsStateWithLifecycle`, or about `Lifecycle.State.STARTED` / `RESUMED` semantics.
12	- 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`.
13
14	## When NOT to use this skill
15
16	- 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.
17	- The data source is already `State<T>` (e.g. `mutableStateOf`, `Animatable.asState()`) — do not wrap it in a flow just to call `collectAsStateWithLifecycle()`.
18	- 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.
19
20	## Prerequisites
21
22	- Compose UI 1.4+ (any modern release).
23	- Add `androidx.lifecycle:lifecycle-runtime-compose` (2.6+; the artifact that exposes `collectAsStateWithLifecycle`). Maven coordinates: `androidx.lifecycle:lifecycle-runtime-compose:<version>`.
24	- Kotlin coroutines basics (`StateFlow`, `SharedFlow`, `conflate`, `distinctUntilChanged`).
25	- Read `../../recomposition/deferring-state-reads/SKILL.md` if the high-frequency emissions are driving animation values — phase deferral may be a better fix than `.conflate()`.
26
27	## Workflow
28
29	1. Audit every `collectAsState()` call. Search the module for `\.collectAsState\(`. Replace each call with `collectAsStateWithLifecycle()` unless the producing flow is created inside the same composable scope.
30	2. Provide an `initialValue` when the flow is not a `StateFlow` (cold `Flow<T>` or `SharedFlow<T>`). For `StateFlow<T>`, the overload reads `.value` — no initial value needed.
31	3. Pick the right `minActiveState`. Default `STARTED` matches the framework's `repeatOnLifecycle` default. Use `RESUMED` for widgets that should only collect while the Activity owns input focus (e.g. always-visible foreground HUD with an aggressive sensor source). Do not use `CREATED` — that defeats the purpose.
32	4. For high-frequency producers (>1 emission per ~100 ms), add `.conflate()` upstream of `collectAsStateWithLifecycle()` so the consumer keeps only the latest value across a frame. If consecutive emissions can be value-equal, also add `.distinctUntilChanged()` — and ensure the emitted type has a correct `equals()`.
33	5. Hoist `Flow<T>` parameters out of composables. Replace `fun Foo(prices: Flow<Price>)` with `fun Foo(price: Price)`. Collect at the caller. If the producer must stay private to the parent, expose a `() -> Price` lambda provider rather than the raw `Flow`.
34	6. For State → Flow direction, use `snapshotFlow { ... }` inside a `LaunchedEffe

People who liked this also viewed

6 picks

Type

collecting-flows-safely

454stars15forks

View on GitHub

How to install collecting-flows-safely?

skydoves/compose-performance-skills/collecting-flows-safely

$npx -y skills add skydoves/compose-performance-skills --skill collecting-flows-safely

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# Collecting Flows Safely — keep upstream work tied to the UI lifecycle
2
3	`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.
4
5	## When to use this skill
6
7	- A `ViewModel` or `Repository` exposes `StateFlow<T>`, `SharedFlow<T>`, or a cold `Flow<T>` to a Compose screen.
8	- The user reports background battery drain, "the screen keeps working when the app is in the recents tray", or wakelock noise on logcat.
9	- A composable consumes sensor data, location, GPS, websocket, or animation frames coming from outside Compose.
10	- A composable's signature is `fun MyScreen(state: Flow<State>)` (Flow-as-parameter antipattern).
11	- The user asks about `collectAsState` vs `collectAsStateWithLifecycle`, or about `Lifecycle.State.STARTED` / `RESUMED` semantics.
12	- 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`.
13
14	## When NOT to use this skill
15
16	- 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.
17	- The data source is already `State<T>` (e.g. `mutableStateOf`, `Animatable.asState()`) — do not wrap it in a flow just to call `collectAsStateWithLifecycle()`.
18	- 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.
19
20	## Prerequisites
21
22	- Compose UI 1.4+ (any modern release).
23	- Add `androidx.lifecycle:lifecycle-runtime-compose` (2.6+; the artifact that exposes `collectAsStateWithLifecycle`). Maven coordinates: `androidx.lifecycle:lifecycle-runtime-compose:<version>`.
24	- Kotlin coroutines basics (`StateFlow`, `SharedFlow`, `conflate`, `distinctUntilChanged`).
25	- Read `../../recomposition/deferring-state-reads/SKILL.md` if the high-frequency emissions are driving animation values — phase deferral may be a better fix than `.conflate()`.
26
27	## Workflow
28
29	1. Audit every `collectAsState()` call. Search the module for `\.collectAsState\(`. Replace each call with `collectAsStateWithLifecycle()` unless the producing flow is created inside the same composable scope.
30	2. Provide an `initialValue` when the flow is not a `StateFlow` (cold `Flow<T>` or `SharedFlow<T>`). For `StateFlow<T>`, the overload reads `.value` — no initial value needed.
31	3. Pick the right `minActiveState`. Default `STARTED` matches the framework's `repeatOnLifecycle` default. Use `RESUMED` for widgets that should only collect while the Activity owns input focus (e.g. always-visible foreground HUD with an aggressive sensor source). Do not use `CREATED` — that defeats the purpose.
32	4. For high-frequency producers (>1 emission per ~100 ms), add `.conflate()` upstream of `collectAsStateWithLifecycle()` so the consumer keeps only the latest value across a frame. If consecutive emissions can be value-equal, also add `.distinctUntilChanged()` — and ensure the emitted type has a correct `equals()`.
33	5. Hoist `Flow<T>` parameters out of composables. Replace `fun Foo(prices: Flow<Price>)` with `fun Foo(price: Price)`. Collect at the caller. If the producer must stay private to the parent, expose a `() -> Price` lambda provider rather than the raw `Flow`.
34	6. For State → Flow direction, use `snapshotFlow { ... }` inside a `LaunchedEffe

People who liked this also viewed

6 picks

Type