From 827d3d66e2e765f9e257c8031a29fe84fc2256e0 Mon Sep 17 00:00:00 2001
From: Tram Bui <trambui@google.com>
Date: Tue, 10 Dec 2024 11:24:53 -0800
Subject: [PATCH] incorporate safe fallback destination to null destination UI
 flickering

---
 .../apps/nowinandroid/ui/NiaAppState.kt       | 19 ++++++++++++++++---
 gradle/libs.versions.toml                     |  2 +-
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppState.kt b/app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppState.kt
index 249f07590..7c892c854 100644
--- a/app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppState.kt
+++ b/app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppState.kt
@@ -18,6 +18,8 @@ package com.google.samples.apps.nowinandroid.ui
 
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.Stable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
 import androidx.navigation.NavController
@@ -25,7 +27,6 @@ import androidx.navigation.NavDestination
 import androidx.navigation.NavDestination.Companion.hasRoute
 import androidx.navigation.NavGraph.Companion.findStartDestination
 import androidx.navigation.NavHostController
-import androidx.navigation.compose.currentBackStackEntryAsState
 import androidx.navigation.compose.rememberNavController
 import androidx.navigation.navOptions
 import androidx.tracing.trace
@@ -83,9 +84,21 @@ class NiaAppState(
     userNewsResourceRepository: UserNewsResourceRepository,
     timeZoneMonitor: TimeZoneMonitor,
 ) {
+    private val previousDestination = mutableStateOf<NavDestination?>(null)
+
     val currentDestination: NavDestination?
-        @Composable get() = navController
-            .currentBackStackEntryAsState().value?.destination
+        @Composable get() {
+            // Collect the currentBackStackEntryFlow as a state
+            val currentEntry = navController.currentBackStackEntryFlow
+                .collectAsState(initial = null)
+
+            // Fallback to previousDestination if currentEntry is null
+            return currentEntry.value?.destination.also { destination ->
+                if (destination != null) {
+                    previousDestination.value = destination
+                }
+            } ?: previousDestination.value
+        }
 
     val currentTopLevelDestination: TopLevelDestination?
         @Composable get() {
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 07076ca7d..7dc96d65a 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -17,7 +17,7 @@ androidxHiltNavigationCompose = "1.2.0"
 androidxLifecycle = "2.8.6"
 androidxMacroBenchmark = "1.3.0"
 androidxMetrics = "1.0.0-beta01"
-androidxNavigation = "2.8.0"
+androidxNavigation = "2.8.4"
 androidxProfileinstaller = "1.3.1"
 androidxTestCore = "1.6.1"
 androidxTestExt = "1.2.1"