Getting arg directly from navBackStackEntry

Composables.kt

@Composable
fun StartScreen(onNavigateClick: (String) -> Unit) {
  Column(
    modifier = Modifier.fillMaxSize(),
    verticalArrangement = Arrangement.Center,
    horizontalAlignment = Alignment.CenterHorizontally,
  ) {
    var argText by rememberSaveable { mutableStateOf("") }
    TextField(
      value = argText,
      onValueChange = { argText = it },
    )
    Button(
      onClick = { onNavigateClick(argText) },
      modifier = Modifier.padding(top = 16.dp),
      enabled = argText.isNotBlank(),
    ) {
      Text(text = "Navigate with arg")
    }
  }
}

@Composable
fun DetailsScreen(arg: String) {
  Box(
    modifier = Modifier.fillMaxSize(),
    contentAlignment = Alignment.Center,
  ) {
    Text(
      text = arg,
      style = typography.headlineMedium,
    )
  }
}

@Composable
fun App(
  modifier: Modifier = Modifier,
) {
  Box(
    modifier = modifier
      .fillMaxSize()
      .background(color = colorScheme.background),
  ) {
    val navController = rememberNavController()
    NavHost(navController = navController, startDestination = "start") {
      composable(route = "start") {
        StartScreen(
          onNavigateClick = { arg -> navController.navigate(route = "details/$arg") },
        )
      }
      composable(route = "details/{arg}") { navBackStackEntry ->
        val arg = requireNotNull(navBackStackEntry.arguments?.getString("arg"))
        DetailsScreen(arg = arg)
      }
    }
  }
}