animateFloatAsState

AlphaAnimationSample

@Composable
fun AlphaAnimationSample() {
    @Composable
    fun alphaAnimation(visible: Boolean) {
        // Animates to 1f or 0f based on [visible].
        // This [animateState] returns a State<Float> object. The value of the State object is
        // being updated by animation. (This method is overloaded for different parameter types.)
        // Here we use the returned [State] object as a property delegate.
        val alpha: Float by animateFloatAsState(if (visible) 1f else 0f)
        // Updates the alpha of a graphics layer with the float animation value. It is more
        // performant to modify alpha in a graphics layer than using `Modifier.alpha`. The former
        // limits the invalidation scope of alpha change to graphicsLayer's draw stage (i.e. no
        // recomposition would be needed). The latter triggers recomposition on each animation
        // frame.
        Box(modifier = Modifier.graphicsLayer { this.alpha = alpha }.background(Color.Red))
    }
}