fix: Prevent multiple navigation when button is clicked in fast succession

Author: flamyoad

app/src/main/java/com/flamyoad/filemanager/ui/FileManagerNavHost.kt

@@ -1,11 +1,17 @@
 package com.flamyoad.filemanager.ui
 
+import androidx.compose.animation.AnimatedContentTransitionScope
 import androidx.compose.animation.EnterTransition
 import androidx.compose.animation.ExitTransition
+import androidx.compose.animation.core.tween
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.compose.dropUnlessResumed
+import androidx.navigation.NavController
 import androidx.navigation.NavHostController
 import androidx.navigation.compose.NavHost
+import com.flamyoad.common.Route
 import com.flamyoad.explorer_impl.FileListRoute
 import com.flamyoad.explorer_impl.HomePageRoute
 import com.flamyoad.explorer_impl.fileListRoute
@@ -20,20 +26,49 @@ fun FileManagerNavHost(
     NavHost(
         navController = navController,
         startDestination = HomePageRoute,
-        enterTransition = { EnterTransition.None },
-        exitTransition = { ExitTransition.None },
+        enterTransition = {
+            slideIntoContainer(
+                AnimatedContentTransitionScope.SlideDirection.Start,
+                tween(500)
+            )
+        },
+        exitTransition = {
+            slideOutOfContainer(
+                AnimatedContentTransitionScope.SlideDirection.Start,
+                tween(500)
+            )
+        },
         modifier = modifier
     ) {
         homePageRoute(
             onNavigateToFileList = { directory ->
-                navController.navigate(FileListRoute(directory))
+                navController.navigateSafely(FileListRoute(directory))
             }
         )
         fileListRoute(
             onNavigateToFileList = { directory ->
-                navController.navigate(FileListRoute(directory))
+                navController.navigateSafely(FileListRoute(directory))
             }
         )
         imageViewerRoute()
     }
+}
+
+// dropUnlessResumed is used to avoid navigating multiple times to the same destination or
+// popping the backstack when the destination is already on top.
+// https://github.com/seve-andre/jetpack-compose-template/pull/37
+//@Composable
+//fun NavController.navigateTo(
+//    route: Route,
+//): () -> Unit = dropUnlessResumed { this.navigate(route) }
+
+
+// https://slack-chats.kotlinlang.org/t/18829110/hey-guys-i-m-trying-to-wrap-my-head-around-the-new-dropunles
+// https://github.com/HedvigInsurance/android/blob/develop/app%2Fapp%2Fsrc%2Fmain%2Fkotlin%2Fcom%2Fhedvig%2Fandroid%2Fapp%2Fnavigation%2FRememberNavigator.kt#L20-L28
+// Pros: Doesn't require @Composable context
+fun NavController.navigateSafely(route: Any) {
+    val currentBackStackEntry = this.currentBackStackEntry ?: return
+    if (currentBackStackEntry.lifecycle.currentState == Lifecycle.State.RESUMED) {
+        this.navigate(route)
+    }
 }

common-ui/src/main/java/com/flamyoad/common_ui/BaseViewModel.kt

@@ -11,11 +11,11 @@ abstract class BaseViewModel: ViewModel() {
 
     fun <T> Flow<T>.toStateFlow(
         initialState: T,
-        stopTimeoutMillis: Long = 500L
+        started: SharingStarted = SharingStarted.WhileSubscribed(stopTimeoutMillis = 5000L),
     ): StateFlow<T> {
             return stateIn(
                 scope = this@BaseViewModel.viewModelScope,
-                started = SharingStarted.WhileSubscribed(stopTimeoutMillis = stopTimeoutMillis),
+                started = started,
                 initialValue = initialState,
             )
     }

explorer-impl/src/main/java/com/flamyoad/explorer_impl/ui/filelist/FileListViewModel.kt

@@ -8,6 +8,7 @@ import com.flamyoad.file_scanner.DirectoryProvider
 import com.flamyoad.file_scanner.FileHandle
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.filterNotNull
@@ -33,7 +34,7 @@ internal class FileListViewModel @Inject constructor(
         .flatMapLatest { directoryProvider.observeDir(it) }
         .map<List<File>, UiState<List<File>>> { UiState.Success(it) } // oh no...we shoul;dnt have to
         .catch { emit(UiState.Error(it)) }
-        .toStateFlow(initialState = UiState.Loading)
+        .toStateFlow(initialState = UiState.Loading, started = SharingStarted.Lazily)
 
     fun initPath(path: File) {
         currentPath.update { path }