Animation Theme

Theme.kt

@Composable
fun ComposeFunctionsTheme(
    darkTheme: Boolean = isSystemInDarkTheme(),
    content: @Composable () -> Unit
) {
    val palette = if (darkTheme) { DarkColorPalette } else { LightColorPalette }

    MaterialTheme(
        colors = palette.switch(),
        typography = Typography,
        shapes = Shapes,
        content = content
    )
}

@Composable
private fun animateColor(targetValue: Color) =
    animateColorAsState(
        targetValue = targetValue,
        animationSpec = tween(durationMillis = 2000)
    ).value

@Composable
fun Colors.switch() = copy(
    primary = animateColor(primary),
    primaryVariant = animateColor(primaryVariant),
    secondary = animateColor(secondary),
    secondaryVariant = animateColor(secondaryVariant),
    background = animateColor(background),
    surface = animateColor(surface),
    error = animateColor(error),
    onPrimary = animateColor(onPrimary),
    onSecondary = animateColor(onSecondary),
    onBackground = animateColor(onBackground),
    onSurface = animateColor(onSurface),
    onError = animateColor(onError)
)