Jetpack Compose - 如果具有嵌套导航，则不会选择底部导航图标

Question

我想要一个带有两个 items/screens 的底部导航栏：订单和帐户。订单是起始目的地。 Order 有自己的导航，它有两个屏幕：ItemList 和 ItemDetail。在 ItemList 屏幕中单击项目时打开 ItemDetail。

当我运行应用程序时，我可以看到 ItemList 屏幕，但未选中底部导航栏中的订单项目。如果我点击帐户项目，我可以看到帐户屏幕，并且在底部导航栏中选择了帐户项目。

我认为这是由于重组而发生的：当在开始时选择订单时，因为它是起始目的地，它的嵌套图被调用并导航到一个新的目的地（ItemList），引导重组，currentRoute 是“itemList”而不是“order”。

如何在底部导航栏中选中订单图标？是否有建议使用底部导航处理嵌套图？

这是我目前拥有的：

object Destinations {
    const val ORDER_ROUTE = "order"
    const val ACCOUNT_ROUTE = "account"
    const val ITEM_LIST_ROUTE = "itemList"
    const val ITEM_DETAIL_ROUTE = "itemDetail"
    const val ITEM_DETAIL_ID_KEY = "itemId"
}

class NavigationActions(navController: NavHostController) {
    val selectItem: (Long) -> Unit = { itemId: Long ->
        navController.navigate("${Destinations.ITEM_DETAIL_ROUTE}/$itemId")
    }
    val upPress: () -> Unit = {
        navController.navigateUp()
    }
}

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

@Compose
fun MyApp() {
    MyAppTheme {
        val navController = rememberNavController()

        val tabs = listOf(Destinations.ORDER_ROUTE, Destinations.ACCOUNT_ROUTE)

        val navBackStackEntry by navController.currentBackStackEntryAsState()
        val currentRoute = navBackStackEntry?.arguments?.getString(KEY_ROUTE)

        Scaffold(
            bottomBar = {
                BottomNavigation {
                    tabs.forEach { tab ->
                        BottomNavigationItem(
                            icon = { Icons.Filled.Favorite },
                            label = { Text(tab) },
                            selected = currentRoute == tab,
                            onClick = {
                                navController.navigate(tab) {
                                    popUpTo = navController.graph.startDestination
                                    launchSingleTop = true
                                }
                            },
                            alwaysShowLabel = true,
                            selectedContentColor = MaterialTheme.colors.secondary,
                            unselectedContentColor = LocalContentColor.current
                        )
                    }
                }
            }
        ) {
            NavGraph(navController)
        }
    }
}

@Composable
fun NavGraph(
    navController: NavHostController,
    startDestination: String = Destinations.ORDER_ROUTE
) {
    val actions = remember(navController) { NavigationActions(navController) }

    NavHost(navController = navController, startDestination = startDestination) {
        navigation(startDestination = Destinations.ITEM_LIST_ROUTE, route = Destinations.ORDER_ROUTE) {
            composable(Destinations.ITEM_LIST_ROUTE) {
                ItemList(actions.selectItem)
            }
            composable(
                "${Destinations.ITEM_DETAIL_ROUTE}/{$Destinations.ITEM_DETAIL_ID_KEY}",
                arguments = listOf(navArgument(Destinations.ITEM_DETAIL_ID_KEY) {
                    type = NavType.LongType
                })
            ) {
                ItemDetail()
            }
        }
        composable(Destinations.ACCOUNT_ROUTE) {
            Account()
        }
    }
}

Answer 1

这是我写的article with a similar example. It's in Portuguese but if you translate the page to English you'll get the idea... Also, you can find the sources here。

我认为问题的发生是因为您对整个应用只使用了一个 NavHost。事实上，我猜你需要为每个标签使用一个NavHost，那么当用户select一个标签时，你必须改变当前的NavHost。

哦！我的文章就是基于这个posthere，也能帮到你

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