simple_animated_fab.kt

@Composable
private fun FabContent(
  modifier: Modifier = Modifier,
) {
  var containerState by remember { mutableStateOf(ContainerState.Fab) }
  AnimatedContent(
    modifier = modifier,
    targetState = containerState,
    label = "container transform",
  ) { state ->
    when (state) {
      ContainerState.Fab -> Fab(
        modifier = Modifier
          .padding(end = 16.dp, bottom = 16.dp),
        onClick = { containerState = ContainerState.Fullscreen }
      )

      ContainerState.Fullscreen -> AddContentScreen(
        onBack = { containerState = ContainerState.Fab }
      )
    }
  }
}