I can post a complete sample project, but I am having some serious performance issues with animateFl...

# compose-android

[dazza5000]

I can post a complete sample project, but I am having some serious performance issues with animateFloatAsValue and LaunchedEffect with the float value as a key. Below is a concise example

[dazza5000]

val angle: Float by animateFloatAsState(
        targetValue = if (animationRunning)
            finalAngle
        else 0f,
        animationSpec = tween(durationMillis = SPIN_DURATION.toInt()),
        label = "AnimateWheel",
    )

    LaunchedEffect(angle) {
        
    }

[dazza5000]

Just setting an empty LaunchedEffect results in like 1000x slower animation

[dazza5000]

noLaunchedEffect.webm

noLaunchedEffect.webm

[dazza5000]

EmptyLaunchedEffect.webm

EmptyLaunchedEffect.webm

[dazza5000]

In the view system we had ValueAnimator.addUpdateListener which didn't appear to have any noticeable performance impact

[Stylianos Gakis]

Why are you restarting an entire LaunchedEffect (which has to cancel the previous work and then start a new coroutine eachtime) on basically every single frame?
What are you trying to do inside that LaunchedEffect that needs to be re-run so often?

[dazza5000]

We vibrate the wheel to simulate a real spin wheel at particular rotations

[dazza5000]

if (newAngle > nextVibrationAngle) {
                    nextVibrationAngle += sliceAngle
                    future?.cancel(true)
                    future = executor.submit {
                        context?.let { VibrationCompat.vibrate(it, EffectType.WHEEL_TICK) }
                    }
                }

[dazza5000]

Here is the compose variant

LaunchedEffect(angle) {
            if (angle > nextVibrationAngle) {
                nextVibrationAngle += sliceAngle
                job?.cancel()
                job = launch {
                    context.let { VibrationCompat.vibrate(it, EffectType.WHEEL_TICK) }
                }

                Log.d("WheelViewCompose", "Vibrating! $nextVibrationAngle")
            }
    }

[dazza5000]

this creates a truly immersive experience 😜

[dazza5000]

Will probably just switch to using a timing approach instead of observing the angle

[dazza5000]

Still concerning that an empty LaunchedEffect has such a significant performance impact

[Ben Trengrove [G]]

Ideally our APIs wouldn't lead you down this path, but that is a misuse of the LaunchedEffect API which is what Stylianos is saying. The way you have written it you are going to be creating and launching a coroutine on every frame because you are using angle as a key

[Ben Trengrove [G]]

Have a look at this example in the animation docs which is close to what you want
https://developer.android.com/jetpack/compose/animation/value-based#targetbasedanimation

[Ben Trengrove [G]]

You probably want animationRunning as your key

[Ben Trengrove [G]]

Something like this will observe the value of angle and not relaunch on every frame

LaunchedEffect(animationRunning) {
   if (animationRunning) {
      snapshotFlow { angle }.collect { angle ->
         // use angle
      }
   }
}

[dazza5000]

will give that a try - thank you ben

[dazza5000]

that worked - thank you Ben