提取Scaffold，部分核心页面才有底部导航栏【但是性能变差了】

app/src/main/java/com/aiosman/riderpro/MainActivity.kt

@@ -12,6 +12,7 @@ import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.WindowInsets
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.height
@@ -63,6 +64,9 @@ val LocalNavController = compositionLocalOf<NavHostController> {
 
 @Composable
 fun NavigationController(navController: NavHostController) {
+    val navigationBarHeight = with(LocalDensity.current) {
+        WindowInsets.navigationBars.getBottom(this).toDp()
+    }
     NavHost(
         navController = navController,
         startDestination = NavigationItem.Home.route,
@@ -72,60 +76,117 @@ fun NavigationController(navController: NavHostController) {
         exitTransition = {
             fadeOut(animationSpec = tween(0))
         }) {
-        composable(route = NavigationItem.Home.route) {
-            Home()
+        // 带底部导航栏的路由：
+        listOf(NavigationItem.Home,
+               NavigationItem.Street,
+               NavigationItem.Add,
+               NavigationItem.Message,
+               NavigationItem.Profile).forEach { item ->
+            composable(route = item.route) {
+                ScaffoldWithNavigationBar(navController) {
+                    when (item) {
+                        NavigationItem.Home -> Home()
+                        NavigationItem.Street -> Street()
+                        NavigationItem.Add -> Add()
+                        NavigationItem.Message -> Video()
+                        NavigationItem.Profile -> Profile()
+                        else -> {} // 由于过滤，这里不会发生
                     }
-        composable(route = NavigationItem.Street.route) {
-            Street()
                 }
-        composable(route = NavigationItem.Add.route) {
-            Add()
             }
-        composable(route = NavigationItem.Message.route) {
-            Video()
-        }
-        composable(route = NavigationItem.Profile.route) {
-            Profile()
         }
         composable(route = "ProfileTimeline") {
+            Box(
+                modifier = Modifier.padding(bottom = navigationBarHeight)
+            ) {
                 GalleryPage()
             }
+        }
         composable(route="LocationDetail") {
+            Box(
+                modifier = Modifier.padding(bottom = navigationBarHeight)
+            ) {
                 LocationDetail()
             }
+        }
         composable(route="OfficialPhoto") {
+            Box(
+                modifier = Modifier.padding(bottom = navigationBarHeight)
+            ) {
                 OfficialGalleryPage()
             }
+        }
         composable(route="OfficialPhotographer") {
+            Box(
+                modifier = Modifier.padding(bottom = navigationBarHeight)
+            ) {
                 OfficialPhotographer()
             }
+        }
         composable(route="Post") {
+            Box(
+                modifier = Modifier.padding(bottom = navigationBarHeight)
+            ) {
                 PostPage()
             }
+        }
         composable(route="ModificationList") {
+            Box(
+                modifier = Modifier.padding(bottom = navigationBarHeight)
+            ) {
                 ModificationListScreen()
             }
+        }
         composable(route="MyMessage") {
+            Box(
+                modifier = Modifier.padding(bottom = navigationBarHeight)
+            ) {
                 NotificationsScreen()
             }
+        }
         composable(route="Comments") {
+            Box(
+                modifier = Modifier.padding(navigationBarHeight)
+            ) {
                 CommentsScreen()
             }
+        }
         composable(route="Likes") {
+            Box(
+                modifier = Modifier.padding(navigationBarHeight)
+            ) {
                 LikePage()
             }
+        }
         composable(route="Followers") {
+            Box(
+                modifier = Modifier.padding(navigationBarHeight)
+            ) {
                 FollowerPage()
             }
         }
+    }
 }
 
 @Composable
 fun Navigation() {
+    val navController = rememberNavController()
+    CompositionLocalProvider(LocalNavController provides navController) {
+        Box {
+            NavigationController(navController = navController)
+        }
+    }
+}
+
+// 用于带导航栏的路由的可复用 composable
+@Composable
+fun ScaffoldWithNavigationBar(
+    navController: NavHostController,
+    content: @Composable () -> Unit
+) {
     val navigationBarHeight = with(LocalDensity.current) {
         WindowInsets.navigationBars.getBottom(this).toDp()
     }
-    val navController = rememberNavController()
     val item = listOf(
         NavigationItem.Home,
         NavigationItem.Street,
@@ -133,13 +194,9 @@ fun Navigation() {
         NavigationItem.Message,
         NavigationItem.Profile
     )
-    CompositionLocalProvider(LocalNavController provides navController) {
     Scaffold(
         modifier = Modifier.statusBarsPadding(),
-            topBar = {},
-
-            bottomBar = {
-                NavigationBar(
+        bottomBar = { NavigationBar(
             modifier = Modifier.height(56.dp + navigationBarHeight),
             containerColor = Color.Black
         ) {
@@ -192,17 +249,15 @@ fun Navigation() {
                     }
                 )
             }
-                }
-            }
-        ) {  it
-            Box(
-                modifier = Modifier.padding(it)
-            ) {
-                NavigationController(navController = navController)
-            }
-        }
-    }
 
+        } }
+    ) { innerPadding ->
+        Box(
+            modifier = Modifier.padding(innerPadding)
+        ) {
+            content()
+        }
+    }
 }
 
 @Composable