Jetpack Composeに馴染みたい

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MyApp {
                MyScreenContent()
            }
        }
    }
}

@Composable
fun MyApp(content: @Composable () -> Unit) {
    ComposeStudyTheme {
        Surface(color = Color.Yellow) {
            content()
        }
    }
}

@Composable
fun Greeting(name: String) {
    var isSelected by remember { mutableStateOf(false) }
    val backgroundColor by animateColorAsState(if (isSelected) Color.Red else Color.Transparent)
    Text(
        text = "Hello $name!",
        modifier = Modifier
            .padding(24.dp)
            .background(color = backgroundColor)
            .clickable(onClick = { isSelected = !isSelected })
    )
}

@Composable
fun Counter(count: Int, updateCount: (Int) -> Unit) {
    Button(
        onClick = { updateCount(count + 1) },
        colors = ButtonDefaults.buttonColors(
            backgroundColor = if (count > 5) Color.Green else Color.White
        )
    ) {
        Text("I've been clicked $count times")
    }
}

@Composable
fun NameList(names: List<String>, modifier: Modifier = Modifier) {
    LazyColumn(modifier = modifier) {
        items(items = names) { name ->
            Greeting(name = name)
            Divider(color = Color.Black)
        }
    }
}

@Composable
fun MyScreenContent(names: List<String> = List(1000) { "HelloAndroid #$it" }) {
    val counterState = remember { mutableStateOf(0) }
    Column(modifier = Modifier.fillMaxHeight()) {
        NameList(names = names, modifier = Modifier.weight(1f))

        Counter(
            count = counterState.value, updateCount = { newCount ->
                counterState.value = newCount
            })
    }
}