[android]Composeのanimate関数

class MainActivity : ComponentActivity() {

    overrider fun onCreate(savedInstanceState: Bundle?){
        super.onCreate(saveInstanceState)
        setContent {
            MaterialTheme {
                AnimatedBoxExample()
            }
        }
    }

    @Composable
    fun AnimatedBoxExample() {
        var expaned by remember {mutableStateOf(false)}

        val boxSize by animateDpAsState(
            targetValue = if(expanded) 200.dp else 100.dp,
            label ="BoxSizeAnimation"
        )

        Column(
            modifier = Modifier
                .fillMaxSize()
                .padding(32.dp),
            verticalArrangement = Arrangement.Center,
            horizontalAlignment = Alignment.CenterHorizontally
        ) {
            Box(
                modifier = Modifier
                    .size(boxSize)
                    .padding(8.dp),
                contentAlignment = Alignment.Center
            ) {
                color = MaterialTheme.colorScheme.primary,
                modifier = Modifier.fillMaxSize()
            } {}
        }
        Spacer(modifier = Modifier.height(16.dp))

        Button(onClick= {expanded = !expanded}) {
            Text(text =if (expanded) "縮小する" else "拡大する")
        }
    }
}

animateDpAsState：Dp 値を滑らかにアニメーションさせます。
targetValue：アニメーションで変化させたい目標値。
expanded を切り替えることで、Boxのサイズが 100.dp ↔ 200.dp にアニメーション付きで変化。