I'm using Navigation Components in jetpack compose. When I navigate to other,onCreate was launch 5,6 times.
It's my application log when I start the app and navigate to other routes ->
2021-09-25 16:40:41.486 28201-28201/ D/HomeScreenKt$HomeScreen: ON_START
2021-09-25 16:40:41.486 28201-28201/ D/HomeScreenKt$HomeScreen: ON_RESUME
2021-09-25 16:40:41.486 28201-28201/ D/HomeScreenKt$HomeScreen: ON_START
2021-09-25 16:40:41.486 28201-28201/ D/HomeScreenKt$HomeScreen: ON_RESUME
2021-09-25 16:40:41.486 28201-28201/ D/HomeScreenKt$HomeScreen: ON_START
2021-09-25 16:40:41.486 28201-28201/ D/HomeScreenKt$HomeScreen: ON_RESUME
2021-09-25 16:40:41.487 28201-28201/ D/HomeScreenKt$HomeScreen: ON_START
2021-09-25 16:40:41.487 28201-28201/ D/HomeScreenKt$HomeScreen: ON_RESUME
2021-09-25 16:40:41.488 28201-28201/ D/HomeScreenKt$HomeScreen: ON_START
2021-09-25 16:40:41.488 28201-28201/ D/HomeScreenKt$HomeScreen: ON_RESUME
2021-09-25 16:40:41.509 28201-28201/ D/HomeScreenKt$HomeScreen: ON_CREATE
2021-09-25 16:40:41.510 28201-28201/ D/HomeScreenKt$HomeScreen: ON_START
2021-09-25 16:40:41.511 28201-28201/ D/HomeScreenKt$HomeScreen: ON_RESUME
2021-09-25 16:40:41.637 28201-28201/ D/HomeScreenKt$HomeScreen: ON_CREATE
2021-09-25 16:40:41.638 28201-28201/ D/HomeScreenKt$HomeScreen: ON_START
2021-09-25 16:40:41.638 28201-28201/ D/HomeScreenKt$HomeScreen: ON_RESUME
2021-09-25 16:40:41.926 28201-28201/ D/HomeScreenKt$HomeScreen: ON_CREATE
2021-09-25 16:40:41.926 28201-28201/ D/HomeScreenKt$HomeScreen: ON_START
2021-09-25 16:40:41.928 28201-28201/ D/HomeScreenKt$HomeScreen: ON_RESUME
2021-09-25 16:40:41.944 28201-28201/ D/HomeScreenKt$HomeScreen: ON_CREATE
2021-09-25 16:40:41.944 28201-28201/ D/HomeScreenKt$HomeScreen: ON_START
2021-09-25 16:40:41.947 28201-28201/ D/HomeScreenKt$HomeScreen: ON_RESUME
It's an application section that was I config navigation components ->
AppTheme{
val appStateHolder = rememberAppStateHolder()
Scaffold(
bottomBar ={
if (appStateHolder.shouldShowBottomBar){
BottomNav(
navigateToRoute = appStateHolder::navigateToBottomBarRoute
)
}
},
scaffoldState = appStateHolder.scaffoldState
) {
NavHost(
navController = appStateHolder.navController,
startDestination = Constants.Navigation.HOME_SCREEN
) {
composable(Constants.Navigation.HOME_SCREEN) { HomeScreen(viewModel = hiltViewModel()) }
composable(Constants.Navigation.MAP_SCREEN) { MapScreen(viewModel = hiltViewModel()) }
composable(Constants.Navigation.LOCATION_SCREEN) { }
composable(Constants.Navigation.CHART_SCREEN) { }
composable(Constants.Navigation.SEARCH_SCREEN) { }
}
}
}
HomeScreen ->
fun HomeScreen(viewModel: HomeViewModel) {
LocalLifecycleOwner.current.lifecycle.addObserver(object : LifecycleEventObserver {
override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
Timber.d(event.name)
}
}
A side-effect is a change to the state of the app that happens outside the scope of a composable function. Due to composables' lifecycle and properties such as unpredictable recompositions, executing recompositions of composables in different orders, or recompositions that can be discarded, composables should ideally be side-effect free.
Adding observable in Compose functions should be used inside a DisposableEffect block and also should be properly removed in onDispose lambda.
@Composable
fun HomeScreen() {
val lifecycleOwner = LocalLifecycleOwner.current
DisposableEffect(this) {
val observer = LifecycleEventObserver { source, event -> Timber.d(event.name) }
lifecycleOwner.lifecycle.addObserver(observer)
onDispose {
lifecycleOwner.lifecycle.removeObserver(observer)
}
}
}
The reason is that recompositions could happen many times. In your case, .addObserver method was called 5-6 times during the recomposition.