Why navBackStackEntry?.destination?.route is returning null? - kotlin

Question

Below is my mainActivity code from my jetpack compose. I'm looking for the current route to show bottom navigation menu accourding to that.
class MainActivity : ComponentActivity(), UIConfiguration {
private var fontFamily = Poppins
var isDarkModeEnable by Delegates.notNull<Boolean>()
companion object {
lateinit var activity: WeakReference<Context>
}
override fun onDestroy() {
super.onDestroy()
activity.clear()
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
activity = WeakReference(this)
isDarkModeEnable = this.resources.configuration.uiMode and
Configuration.UI_MODE_NIGHT_MASK == Configuration.UI_MODE_NIGHT_YES
setContent {
MonoTheme {
// A surface container using the 'background' color from the theme
Surface(
modifier = Modifier.fillMaxSize(),
color = MaterialTheme.colors.background
) {
MainScreen(rememberNavController())
}
}
}
}
override fun onConfigurationChanged(newConfig: Configuration) {
super.onConfigurationChanged(newConfig)
isDarkModeEnable =
newConfig.uiMode and Configuration.UI_MODE_NIGHT_MASK == Configuration.UI_MODE_NIGHT_YES
textStyle(
fontFamily = fontFamily,
lightColor = Color.Blue,
darkColor = Color.White
)
}
override fun textStyle(
fontFamily: FontFamily,
lightColor: Color,
darkColor: Color
) {
val fontColor = darkColor.takeIf { isDarkModeEnable } ?: lightColor
uiElements.apply {
large = TextStyle(
fontFamily = fontFamily,
fontWeight = FontWeight.ExtraBold,
fontSize = 56.sp,
color = fontColor
)
h1 = TextStyle(
fontFamily = fontFamily,
fontWeight = FontWeight.Normal,
fontSize = 32.sp,
color = fontColor
)
h2 = TextStyle(
fontFamily = fontFamily,
fontWeight = FontWeight.Bold,
fontSize = 24.sp,
color = fontColor
)
subtitle1 = TextStyle(
fontFamily = fontFamily,
fontWeight = FontWeight.SemiBold,
fontSize = 20.sp,
color = fontColor
)
subtitle2 = TextStyle(
fontFamily = fontFamily,
fontWeight = FontWeight.SemiBold,
fontSize = 16.sp,
color = fontColor
)
body1 = TextStyle(
fontFamily = fontFamily,
fontWeight = FontWeight.Normal,
fontSize = 16.sp,
color = fontColor
)
button = TextStyle(
fontFamily = fontFamily,
fontWeight = FontWeight.SemiBold,
fontSize = 16.sp,
color = fontColor
)
caption = TextStyle(
fontFamily = fontFamily,
fontWeight = FontWeight.Normal,
fontSize = 12.sp,
color = fontColor
)
bottomBar = TextStyle(
fontFamily = fontFamily,
fontWeight = FontWeight.Normal,
fontSize = 10.sp,
color = fontColor
)
}
this#MainActivity.recreate()
}
#Composable
private fun MainScreen(
navHostController: NavHostController
) {
val showBnm = showBnm(navHostController)
Scaffold(
bottomBar = {
if (showBnm) {
BottomNavigationView(navController = navHostController)
}
},
) {
it.calculateTopPadding()
Column(modifier = Modifier.padding(bottom = if (showBnm) 58.dp else 0.dp)) {
SetupNavGraph(rememberNavController())
}
}
}
#Composable
private fun showBnm(navHostController: NavHostController): Boolean {
return when (currentRoute(navHostController)) {
Screens.Intro.route -> true
Screens.Input.route -> true
Screens.Report.route -> true
Screens.Setting.route -> true
else -> false
}
}
#Composable
private fun BottomNavigationView(navController: NavHostController) {
val items = listOf(
Screens.Input, Screens.Report, Screens.Setting
)
BottomNavigation(
/**modifier = Modifier
.padding(10.dp)
.graphicsLayer(
shape = RoundedCornerShape(topStart = 25.dp, topEnd = 25.dp),
clip = true,
),*/
backgroundColor = colorResource(
id = R.color.background
),
contentColor = colorResource(
id = R.color.bottomBarIcon
),
) {
val navBackStackEntry by navController.currentBackStackEntryAsState()
val currentRoute = navBackStackEntry?.destination?.route
items.forEach { item ->
BottomNavigationItem(icon = {
Icon(
painterResource(id = item.selectedIcon.takeIf {
currentRoute == item.route
} ?: item.notSelectedIcon),
contentDescription
= item.name
)
}, label = {
Text(
text = item.name, style = uiElements.bottomBar
)
},
selectedContentColor = colorResource(id = R.color.bottomBarIcon),
unselectedContentColor = colorResource(id = R.color.bottomBarIcon),
alwaysShowLabel = true,
selected = currentRoute == item.route,
onClick = {
navController.navigate(item.route) {
navController.graph.startDestinationRoute?.let { route ->
popUpTo(route) {
inclusive = true
saveState = true
}
}
launchSingleTop = true
restoreState = true
}
})
}
}
}
#Composable
private fun currentRoute(navHostController: NavHostController): String? {
val navBackStackEntry by navHostController.currentBackStackEntryAsState()
return navBackStackEntry?.destination?.route
}
#Preview()
#Composable
fun Bnm() = MainScreen(rememberNavController())
}
This is the currentRoute
#Composable
private fun currentRoute(navHostController: NavHostController): String? {
val navBackStackEntry by navHostController.currentBackStackEntryAsState()
return navBackStackEntry?.destination?.route
}
This function suppose to return the route of current destination but it is returning null. Therefore, I'm not be able to get the desired result.