Introductory Bounce Effect

IntroBounce.kt

val backdropState = rememberBackdropScaffoldState(Revealed)
var offset by (backdropState.offset as MutableState)

// Optional conditions: ex. should-bounce flag, data-loading finished, etc.
if (backdropState.isRevealed) { 
  // remember the original offset position to go back to
  val revealedOffset = remember { backdropState.offset.value }
  // value holder Animatable for the actual offset
  val offsetAnimatable = remember { Animatable(revealedOffset) }
  
  LaunchedEffect(Unit) {
    // lift up by 150 pixels with tween animation spec 
    offsetAnimatable.animateTo(
      targetValue = revealedOffset - 150,
      animationSpec = tween(800)
    )
    // drop down back to original offset with spring animation spec
    offsetAnimatable.animateTo(
      targetValue = revealedOffset,
      animationSpec = spring(
        dampingRatio = 0.4f,
        stiffness = Spring.StiffnessLow
      )
    )
  }
  // drive offset mutableState with Animatable values
  offset = offsetAnimatable.value
}