AnimatedVisibilityPost1.kt

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            ComposePlaygroundTheme {
                Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.background) {
                    var name by remember { mutableStateOf<String?>("Hello World") }

                    Column(
                        modifier = Modifier.fillMaxSize(),
                        verticalArrangement = Arrangement.Center,
                        horizontalAlignment = Alignment.CenterHorizontally
                    ) {
                        Greeting(name)

                        Button(onClick = {
                            name = if (name == null) "Hello World" else null
                        }) {
                            Text(text = "Change greeting")
                        }
                    }
                }
            }
        }
    }
}

@Composable
fun Greeting(name: String?) {
    if (name != null) Text(text = name)
}