Merge pull request #468 from JoseAlcerreca/owl_multiple_nav_fix

[Owl] Fixes multiple navigation calls with simultaneous taps

Author: JoseAlcerreca

Owl/app/src/main/java/com/example/owl/ui/NavGraph.kt

@@ -21,6 +21,8 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
+import androidx.lifecycle.Lifecycle
+import androidx.navigation.NavBackStackEntry
 import androidx.navigation.NavHostController
 import androidx.navigation.NavType
 import androidx.navigation.compose.NavHost
@@ -83,7 +85,7 @@ fun NavGraph(
             startDestination = CourseTabs.FEATURED.route
         ) {
             courses(
-                onCourseSelected = actions.selectCourse,
+                onCourseSelected = actions.openCourse,
                 onboardingComplete = onboardingComplete,
                 navController = navController,
                 modifier = modifier
@@ -94,12 +96,15 @@ fun NavGraph(
             arguments = listOf(
                 navArgument(COURSE_DETAIL_ID_KEY) { type = NavType.LongType }
             )
-        ) { backStackEntry ->
+        ) { backStackEntry: NavBackStackEntry ->
             val arguments = requireNotNull(backStackEntry.arguments)
+            val currentCourseId = arguments.getLong(COURSE_DETAIL_ID_KEY)
             CourseDetails(
-                courseId = arguments.getLong(COURSE_DETAIL_ID_KEY),
-                selectCourse = actions.selectCourse,
-                upPress = actions.upPress
+                courseId = currentCourseId,
+                selectCourse = { newCourseId ->
+                    actions.relatedCourse(newCourseId, backStackEntry)
+                },
+                upPress = { actions.upPress(backStackEntry) }
             )
         }
     }
@@ -112,10 +117,36 @@ class MainActions(navController: NavHostController) {
     val onboardingComplete: () -> Unit = {
         navController.popBackStack()
     }
-    val selectCourse: (Long) -> Unit = { courseId: Long ->
-        navController.navigate("${MainDestinations.COURSE_DETAIL_ROUTE}/$courseId")
+
+    // Used from COURSES_ROUTE
+    val openCourse = { newCourseId: Long, from: NavBackStackEntry ->
+        // In order to discard duplicated navigation events, we check the Lifecycle
+        if (from.lifecycleIsResumed()) {
+            navController.navigate("${MainDestinations.COURSE_DETAIL_ROUTE}/$newCourseId")
+        }
     }
-    val upPress: () -> Unit = {
-        navController.navigateUp()
+
+    // Used from COURSE_DETAIL_ROUTE
+    val relatedCourse = { newCourseId: Long, from: NavBackStackEntry ->
+        // In order to discard duplicated navigation events, we check the Lifecycle
+        if (from.lifecycleIsResumed()) {
+            navController.navigate("${MainDestinations.COURSE_DETAIL_ROUTE}/$newCourseId")
+        }
+    }
+
+    // Used from COURSE_DETAIL_ROUTE
+    val upPress: (rom: NavBackStackEntry) -> Unit = { from ->
+        // In order to discard duplicated navigation events, we check the Lifecycle
+        if (from.lifecycleIsResumed()) {
+            navController.navigateUp()
+        }
     }
 }
+
+/**
+ * If the lifecycle is not resumed it means this NavBackStackEntry already processed a nav event.
+ *
+ * This is used to de-duplicate navigation events.
+ */
+private fun NavBackStackEntry.lifecycleIsResumed() =
+    this.lifecycle.currentState == Lifecycle.State.RESUMED

Owl/app/src/main/java/com/example/owl/ui/courses/Courses.kt

@@ -34,6 +34,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
+import androidx.navigation.NavBackStackEntry
 import androidx.navigation.NavGraphBuilder
 import androidx.navigation.NavHostController
 import androidx.navigation.compose.composable
@@ -44,24 +45,32 @@ import com.example.owl.model.topics
 import com.example.owl.ui.MainDestinations
 
 fun NavGraphBuilder.courses(
-    onCourseSelected: (Long) -> Unit,
+    onCourseSelected: (Long, NavBackStackEntry) -> Unit,
     onboardingComplete: State<Boolean>, // https://issuetracker.google.com/174783110
     navController: NavHostController,
     modifier: Modifier = Modifier
 ) {
-    composable(CourseTabs.FEATURED.route) {
+    composable(CourseTabs.FEATURED.route) { from ->
         // Show onboarding instead if not shown yet.
         LaunchedEffect(onboardingComplete) {
             if (!onboardingComplete.value) {
                 navController.navigate(MainDestinations.ONBOARDING_ROUTE)
             }
         }
         if (onboardingComplete.value) { // Avoid glitch when showing onboarding
-            FeaturedCourses(courses, onCourseSelected, modifier)
+            FeaturedCourses(
+                courses = courses,
+                selectCourse = { id -> onCourseSelected(id, from) },
+                modifier = modifier
+            )
         }
     }
-    composable(CourseTabs.MY_COURSES.route) {
-        MyCourses(courses, onCourseSelected, modifier)
+    composable(CourseTabs.MY_COURSES.route) { from ->
+        MyCourses(
+            courses = courses,
+            { id -> onCourseSelected(id, from) },
+            modifier
+        )
     }
     composable(CourseTabs.SEARCH.route) {
         SearchCourses(topics, modifier)