Android jetpack compose countdown animation

Question

Is it possible to make an animation like gif with Jetpack Compose?

Answer 1

One of the ways to do is using Animatables that animate scale and alpha after each other.

create a class that contains 2 Animatables

class AnimatedCountdownTimer(
    private val coroutineScope: CoroutineScope
) {

    private val animatableScale = Animatable(1f)
    private val animatableAlpha = Animatable(1f)

    val scale: Float
        get() = animatableScale.value

    val alpha: Float
        get() = animatableAlpha.value

    fun start(initialValue: Int, endValue: Int, onChange: (Int) -> Unit) {

        var value = initialValue

        coroutineScope.launch {
            while (value > endValue - 1) {
                onChange(value)
                animatableScale.snapTo(1f)
                animatableAlpha.snapTo(1f)
                animatableScale.animateTo(2f, animationSpec = tween(750))
                animatableAlpha.animateTo(0f, animationSpec = tween(250))
                value--

            }
        }
    }
}

And use it as

@Preview
@Composable
fun TimerTest() {


    var timer by remember {
        mutableStateOf(5)
    }

    val coroutineScope = rememberCoroutineScope()

    val animatedCountdownTimer = remember {
        AnimatedCountdownTimer(coroutineScope)
    }

    Column(
        modifier = Modifier.fillMaxSize().padding(16.dp),
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        Text(
            modifier = Modifier.graphicsLayer {
                scaleX = animatedCountdownTimer.scale
                scaleY = animatedCountdownTimer.scale
                alpha = animatedCountdownTimer.alpha
            },
            text = "$timer",
            fontSize = 120.sp,
            fontWeight = FontWeight.Bold,
            color = Color.Gray
        )
        Spacer(Modifier.height(20.dp))
        Button(
            modifier = Modifier.fillMaxWidth(),
            onClick = {
                animatedCountdownTimer.start(5, 0) {
                    timer = it
                }
            }
        ) {
            Text("Start")
        }
    }
}

If you don't want to scale to 1f after animation end just ad if block so it can stay at scale. Any param can be customized easily time durations or max scale.

If you wish to keep last number scaled you can use it like this

  coroutineScope.launch {
        while (value > endValue - 1) {
            onChange(value)
            animatableScale.snapTo(1f)
            animatableAlpha.snapTo(1f)
            animatableScale.animateTo(2f, animationSpec = tween(750))
            if (value > endValue) {
                animatableAlpha.animateTo(0f, animationSpec = tween(250))
            }
            value--
        }
    }