[英]Jetpack Compose + Navigation - Nested navigation with BottomNavBar
我正在尝试使用 Jetpack Compose + Jetpack Navigation 实现以下屏幕流程:
实际上,我可以编写两个单例:
我无法对整个问题进行编码。 事实上,我对 NavHost 的管理有疑问。 在第一种情况下(SplashScreen -> HomeScreen)我需要在 scope 高位调用 NavHost:
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
MyAppTheme {
//init the Navigation Controller for screen navigation
val navController = rememberNavController()
//setup the Navigation Graph
SetupNavGraph(navController)
而在第二种情况下,我需要在Scaffold
可组合项的innerPadding
scope 中调用它:
fun MainScreen(navController: NavHostController) {
Scaffold(
bottomBar = {
BottomNavBar(navController)
}
) { //innerPadding scope
//setup the Navigation Graph
SetupNavGraph(navController)
}
}
请假设 SetupNavGraph SetupNavGraph()
function 按预期工作(调用NavHost
生成导航树)
NavHost
但没有成功。setContent()
中设置NavHost
,我就可以加载闪屏并移动到空的BottomNavBar
屏幕。 如果我单击BottomNavElements
,我可以导航到子选项卡(在上面的示例中“收藏夹”、“音乐”、“地点”、“新闻”)但是BottomNavBar
消失了innerPadding
scope 中设置NavHost
,因为它仅在切换到主屏幕后才加载(在上面的示例中“Favorite Tab”+ BottomBarNav) 我发现的唯一解决方法是在每个 BottomNav 子选项卡中生成BottomNavBar
可组合项,但这会生成我想避免的可见过渡效果,而且通常这似乎不是一个好的做法。
好的,我找到了解决方案。 这是实现预期结果的步骤:
const val ROOT_ROUTE = "root"
@Composable
fun SetupRootNavGraph(navController: NavHostController) {
NavHost(
navController = navController,
startDestination = Screen.FirstScreen.route,
route = ROOT_ROUTE
) {
composable(Screen.FirstScreen.route) { FirstScreen(navController)}
composable(Screen.SecondScreen.route) { MainScreen(navController)}
}
}
const val BOTTOM_BAR_ROUTE = "bottomBar"
@Composable
fun SetupNavGraphBottomBar(navController: NavHostController) {
NavHost(
navController = navController,
startDestination = BottomBarScreen.FirstElement.route,
route = BOTTOM_BAR_ROUTE
) {
composable(BottomBarScreen.FirstElement.route) { FirstElementScreen() }
composable(BottomBarScreen.SecondElement.route) { SecondElementScreen() }
composable(BottomBarScreen.ThirdElement.route) { ThirdElementScreen() }
}
}
MainActivity
中的setContent()
之后初始化NavController
和RootNavGraph
。 这将负责 SplashScreen -> MainScreen 导航树。class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
MyAppTheme {
//init the Navigation Controller for screen navigation
val navController = rememberNavController()
//setup the Root Navigation Graph
SetupRootNavGraph(navController)
}
}
}
}
NavController
,并在innerPadding
BottomNavGraph
中为其分配 BottomNavGraph。@Composable
fun MainScreen(navController: NavHostController) {
//Re-initialize the NavController to set a new NavGraph
val navControllerBottomBar = rememberNavController()
Scaffold(
bottomBar = {
BottomNavBar(navControllerBottomBar)
}
) {
//setup the Navigation Graph
SetupNavGraphBottomBar(navControllerBottomBar, user)
}
}
这会很有魅力! 当然,您需要构建BottomNavBar
以管理官方文档中记录的导航
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