Navigation3

// build.gradle.kts
dependencies {

    implementation("androidx.navigation3:navigation3-runtime:1.0.0-alpha08")
    implementation("androidx.navigation3:navigation3-ui:1.0.0-alpha08")

    // Lifecycle integration
    implementation("androidx.lifecycle:lifecycle-viewmodel-navigation3:2.9.2")

    // Serialization
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.8.1")
}

// Enable serialization plugin
plugins {
    kotlin("plugin.serialization") version "2.2.0"
}

import kotlinx.serialization.Serializable

@Serializable
data object Home

@Serializable
data class Profile(
    val userId: String
)

@Serializable
data class Product(
    val productId: String,
    val showReviews: Boolean = false
)

@Serializable
data object Settings

@Composable
fun MyApp() {

    val backStack = remember {
        mutableStateListOf<Any>(Home)
    }

    AppNavDisplay(backStack)
}

@Composable
fun AppNavDisplay(
    backStack: SnapshotStateList<Any>
) {

    NavDisplay(
        backStack = backStack,
        onBack = {
            if (backStack.size > 1) {
                backStack.removeLast()
            }
        }
    ) { key ->

        when (key) {

            Home ->
                HomeScreen(
                    onProfileClick = {
                        backStack += Profile(it)
                    }
                )

            is Profile ->
                ProfileScreen(
                    userId = key.userId
                )

            is Product ->
                ProductScreen(
                    productId = key.productId,
                    showReviews = key.showReviews
                )

            Settings ->
                SettingsScreen()
        }
    }
}

backStack += Profile("user123")

backStack.removeLast()

backStack[backStack.lastIndex] = Home

backStack.clear()
backStack += Home

while (backStack.size > 1) {
    backStack.removeLast()
}

when (val key = currentKey) {

    is Profile -> {
        ProfileScreen(
            userId = key.userId
        )
    }

    is Product -> {
        ProductScreen(
            productId = key.productId
        )
    }
}

// CORRECT
backStack += Profile(user.id)

// Fetch object inside ViewModel
class ProfileViewModel(
    savedStateHandle: SavedStateHandle,
    repository: UserRepository
) : ViewModel() {

    val profile = savedStateHandle.toRoute<Profile>()

    val user =
        repository.getUser(profile.userId)
}

// INCORRECT

backStack += User(...)
backStack += ProductRepository(...)
backStack += ProductViewModel(...)

NavDisplay(

    backStack = backStack,

    entryDecorators = listOf(

        rememberSceneSetupNavEntryDecorator(),

        rememberSavedStateNavEntryDecorator(),

        rememberViewModelStoreNavEntryDecorator()
    )

) { key ->

    // destinations
}

class ProfileViewModel(
    savedStateHandle: SavedStateHandle
) : ViewModel() {

    val profile =
        savedStateHandle.toRoute<Profile>()
}

rememberSceneSetupNavEntryDecorator()

rememberSavedStateNavEntryDecorator()

rememberViewModelStoreNavEntryDecorator()

NavDisplay(

    backStack = backStack,

    sceneStrategy = rememberListDetailSceneStrategy()

)

fun handleDeepLink(uri: Uri) {

    val userId =
        uri.lastPathSegment ?: return

    backStack += Profile(userId)
}

NavDisplay(

    backStack = backStack,

    transitionSpec = {

        fadeIn() togetherWith fadeOut()

    }
)