compose-animations

name	compose-animations
description	Use when writing or reviewing Jetpack Compose motion: visibility enter/exit, animating one property toward a target, color or size transitions, multiple properties from one state, switching composable content, or choosing between AnimatedVisibility, animate*AsState, rememberTransition, AnimatedContent, and Crossfade.

Compose: animations

Core principle

Pick the smallest API that matches the problem: built-in visibility and layout transitions first, then a single animated value, then a shared transition object when several values must move together, then gesture-level or imperative APIs when the framework cannot express the motion.

Review procedure

1. Identify the visual job: show/hide, one value, coordinated values, content swap, size change, or gesture-driven motion.
2. Choose the smallest API from the table below.
3. Check lifecycle semantics: should hidden content leave composition, keep focus/state, or only become transparent?
4. Check identity: for state-holder wrappers, choose AnimatedContent.contentKey by visual shape rather than payload churn.
5. Check performance: keep frame-rate animation values as State and read them in layout/draw block modifiers when possible.
6. Escalate to Animatable or lower-level APIs only when target-state animation cannot express the motion.

Pick the smallest animation API

Need	API
Show or hide a subtree with enter/exit semantics; content is removed after exit completes	AnimatedVisibility
Animate one property toward a target derived from state	animateFloatAsState / animateDpAsState / animateColorAsState / animateOffsetAsState / …
Several animated values keyed off one boolean, enum, or sealed state	rememberTransition + transition child animations (animateFloat, animateDp, animateColor, animateValue, …)
Smooth size when child layout height/width changes (e.g. text wraps)	Modifier.animateContentSize()
Swap between different composable trees for the same slot	AnimatedContent or Crossfade
User-driven motion (drag, fling, interruptible springs)	Animatable and related coroutine APIs (see Advanced pointers)

Appear and disappear

Prefer AnimatedVisibility when the UI should leave or join the tree with enter/exit transitions.

AnimatedVisibility(visible = expanded) {
    Text("Details…")
}

animateFloatAsState on alpha only fades; the composable stays in composition and continues to participate in layout unless you gate it yourself. Use that tradeoff when you intentionally keep children mounted (state, focus) but visually hidden. For true remove-from-tree behavior, use AnimatedVisibility (or conditional composition with AnimatedVisibility / AnimatedContent patterns from the quick guide).

Background color

Use animateColorAsState for smooth color targets.

For animated fills behind children, the quick guide recommends drawing with Modifier.drawBehind rather than Modifier.background() so the animated color is applied in the draw phase appropriately for performance.

val background = animateColorAsState(
    targetValue = if (selected) selectedColor else idleColor,
    label = "background",
)
Box(
    Modifier.drawBehind { drawRect(background.value) },
) { /* content */ }

Size changes

Modifier.animateContentSize() animates layout size changes—common for expanding/collapsing text or dynamic chips—without hand-rolling width/height animations.

Value-based animations (animate*AsState)

Compose provides animate*AsState for Float, Dp, Color, Size, Offset, Rect, Int, IntOffset, IntSize, and more. You supply the target; the API owns the animation state.

• Pass an AnimationSpec via animationSpec (e.g. spring, tween) when defaults are wrong for the UI.
• Set a distinct label for debugging and tooling when multiple animations exist in one composable.
• For completion or sequencing details, see Value-based animations.

val width by animateDpAsState(
    targetValue = if (expanded) 200.dp else 56.dp,
    animationSpec = spring(dampingRatio = 0.7f, stiffness = Spring.StiffnessMedium),
    label = "fabWidth",
)

Multiple properties: rememberTransition

When one piece of state (e.g. enum class Phase { A, B, C }) should drive several animated values in lockstep, use rememberTransition and define child animations on that transition:

val transition = rememberTransition(targetState = phase, label = "phase")
val alpha by transition.animateFloat(label = "alpha") { target ->
    if (target == Phase.Visible) 1f else 0f
}
val offset by transition.animateDp(label = "offset") { target ->
    if (target == Phase.Visible) 0.dp else 24.dp
}

Avoid multiple independent animate*AsState calls that should stay visually synchronized but can drift if specs or targets diverge. Older code may use updateTransition; prefer rememberTransition for new code.

Choosing between content-level APIs

Use the official Choose an animation API tree when the table is not enough. Compressed rules:

Situation	Prefer
Same composable, different target values for layout properties	animate*AsState or rememberTransition
Different composable content for the same region (tabs, steps)	AnimatedContent (custom transitionSpec, contentKey) or simpler Crossfade
Pager-like swipe between pages	Horizontal pager APIs from the animation docs / Material—follow the choose-api guidance
Transitions owned by Navigation Compose	Use navigation’s built-in transitions rather than bolting AnimatedContent on top of the same destination swap

Art-based motion (illustrations, Lottie, complex vector timelines) is outside this skill; use dedicated libraries.

Decision flow (high level)

flowchart TD
  start[Animation_need]
  start --> showHide{Show_or_hide_subtree}
  showHide -->|yes| av[AnimatedVisibility]
  showHide -->|no| oneProp{Single_property_to_target}
  oneProp -->|yes| asState["animate*AsState"]
  oneProp -->|no| multiProp{Many_props_one_state}
  multiProp -->|yes| rt[rememberTransition]
  multiProp -->|no| swapTree{Different_composable_content}
  swapTree -->|yes| ac[AnimatedContent_or_Crossfade]
  swapTree -->|no| advanced[Animatable_or_lower_level]

AnimatedContent keys for state holders

When AnimatedContent receives a state-holder wrapper such as AsyncResult<T>, Result<T>, or a sealed UiState, decide what should actually trigger the transition. Usually the animation should run when the content shape changes (loading → content → error), not when the payload inside the same shape changes.

Use contentKey to map rich state to the animation identity:

AnimatedContent(
    targetState = result,
    contentKey = { state ->
        when (state) {
            AsyncResult.Loading -> "loading"
            is AsyncResult.Success -> "content"
            is AsyncResult.Error -> "error"
        }
    },
    label = "profile-content",
) { state ->
    when (state) {
        AsyncResult.Loading -> Loading()
        is AsyncResult.Success -> Profile(state.value)
        is AsyncResult.Error -> ErrorMessage(state.throwable)
    }
}

Without contentKey, every unequal Success(value) can be treated as new content. That is useful if a payload change should animate, but noisy when fresh data updates the same screen shape.

Choose keys by visual shape:

State change	Typical contentKey
Loading → Success → Error	Branch key: "loading", "content", "error"
Success item A → Success item B should crossfade	Stable item id
Success data refresh should update in place	Constant content key for Success
Error message text changes but error UI shape stays	Constant content key for Error

Animated values and composition performance

animate*AsState returns State that updates frequently. If that value feeds Modifier.offset, Modifier.graphicsLayer, scroll-adjacent layout, or other frame-rate paths, avoid reading it in the composable body with by and then passing it into value-form modifiers—use deferred reads (block modifiers, draw/ layout lambdas) instead. See Compose performance.

If recomposition counters spike during motion unrelated to bad stability, see Compose performance.

Escalation points

Load the official docs when one of these applies:

Need	Start with
API tree is still ambiguous	Choose an animation API
Gesture-driven, interruptible, or cancelable motion	Animatable, pointer input, decay
Infinite or repeating cycles	rememberInfiniteTransition
Seekable or test-controlled progress	SeekableTransitionState and related APIs

Common mistakes

Mistake	Fix
Fade with animateFloatAsState(alpha) but expect children to unmount	Use AnimatedVisibility or remove the subtree from composition when hidden
Three animateDpAsState calls that must stay in sync with one enum	One rememberTransition + child animations
Animated color on Modifier.background causing extra work	Prefer drawBehind { drawRect(animatedColor) } per quick guide
Chaining LaunchedEffect + manual Animatable for simple target animation	Prefer animate*AsState or rememberTransition unless gestures require Animatable
Ignoring Navigation’s own transitions	Use Nav APIs for destination transitions; do not duplicate with AnimatedContent for the same swap
AnimatedContent(targetState = asyncResult) animates on every data refresh	Add contentKey based on the visual shape or stable item identity

When not to use this skill

• Side-effect timing (LaunchedEffect, clicks launching work): use Compose state and effects.
• Deep performance tuning of where snapshot state is read: use Compose performance as the primary reference.