我在 Jetpack Compose 中遇到了一些导航回栈的问题。下图是我想要的场景。
我有底栏和两个项目 Home 和 Setting。我想把两者都做成嵌套图。在 HomeNavGraph 中,HomeRootScreen 是 startDestination,可以导航到 HomeDetail1Screen 和 HomeDetail2。设置选项卡也喜欢这样。我想保存那些嵌套的图形状态,例如当我单击 HomeRoot -> HomeDetail1 -> HomeDetail2 时,我单击 BottomBar 中的设置选项卡。然后单击返回主页,我希望我当前的屏幕为 HomeDeatil2Screen。
以下是我的代码。这是我的目的地课程。
sealed class Destinations(
val route: String
) {
object HomeRoot : Destinations(route = "home_root_screen")
object HomeDetail1 : Destinations(route = "home_detail1_screen")
object HomeDetail2 : Destinations(route = "home_detail2_screen")
object SettingRoot : Destinations(route = "setting_root_screen")
object SettingDetail1 : Destinations(route = "setting_detail1_screen")
object SettingDetail2 : Destinations(route = "setting_detail2_screen")
}
const val BOTTOM_NAV_ROUTE = "btn_nav"
const val HOME_ROUTE = "home"
const val SETTING_ROUTE = "setting"
这是我的 BottomBarNavGraph。
@Composable
fun BottomBarNavGraph(
navController: NavHostController
) {
NavHost(
navController = navController,
startDestination = HOME_ROUTE,
route = BOTTOM_NAV_ROUTE
) {
homeNavGraph(navController)
settingNavGraph(navController)
}
}
这是 HomeNavGraph。
fun NavGraphBuilder.homeNavGraph(
navController: NavHostController
) {
navigation(
startDestination = Destinations.HomeRoot.route,
route = HOME_ROUTE
) {
composable(route = Destinations.HomeRoot.route) { HomeScreen(navController = navController) }
composable(route = Destinations.HomeDetail1.route + "/{argText}") {
val arg = it.arguments?.getString("argText") ?: "Nothing Typed"
HomeDetail1Screen(
text = arg,
navController = navController
)
}
composable(route = Destinations.HomeDetail2.route) { HomeDetail2Screen(navController = navController) }
}
}
这是设置导航图。
fun NavGraphBuilder.settingNavGraph(
navController: NavHostController
) {
navigation(
startDestination = Destinations.SettingRoot.route,
route = SETTING_ROUTE
) {
composable(
route = Destinations.SettingRoot.route
) {
SettingScreen(navController = navController)
}
composable(
route = Destinations.SettingDetail1.route
) {
SettingDetail1Screen(navController = navController)
}
composable(
route = Destinations.SettingDetail2.route
) {
SettingDetail2Screen(navController = navController)
}
}
}
这是我的 BottomBarDestinations。
sealed class BottomBarDestinations(
val route: String,
val title: String,
val icon: ImageVector
) {
object Home : BottomBarDestinations(
route = HOME_ROUTE,
title = "Home",
icon = Icons.Default.Home
)
object Setting : BottomBarDestinations(
route = SETTING_ROUTE,
title = "Setting",
icon = Icons.Default.Settings
)
}
以下是我在 navHost 中设置的 BottomBar。
@Composable
fun BottomBar(navController: NavHostController) {
val screens = listOf(
BottomBarDestinations.Home,
BottomBarDestinations.Setting
)
val navBackStackEntry by navController.currentBackStackEntryAsState()
val currentDestinations = navBackStackEntry?.destination
BottomNavigation {
screens.forEach {
AddItem(
screen = it,
currentDestinations = currentDestinations,
navController = navController
)
}
}
}
@Composable
fun RowScope.AddItem(
screen: BottomBarDestinations,
currentDestinations: NavDestination?,
navController: NavHostController
) {
BottomNavigationItem(
label = {
Text(text = screen.title)
},
icon = {
Icon(
imageVector = screen.icon,
contentDescription = "Nav Icon"
)
},
selected = currentDestinations?.hierarchy?.any { it.route == screen.route } == true,
unselectedContentColor = LocalContentColor.current.copy(
alpha = ContentAlpha.disabled
),
onClick = {
navController.navigate(screen.route) {
popUpTo(navController.graph.findStartDestination().id)
launchSingleTop = true
restoreState = true
}
}
)
}
@Composable
fun MainScreen(
) {
val navController = rememberNavController()
Scaffold(bottomBar = {
BottomBar(navController = navController)
}) {
BottomBarNavGraph(navController = navController)
}
}
请帮我解决一下这个。我和这个叠加。如果你想查看源代码。你可以在分支中检查这个
bottom_nav_graph
https://github.com/kyawlinnthant/JetpackComposeNavigationComponent/tree/nested_graph