add an extra function for making sure we show all required folders

app/src/main/kotlin/com/simplemobiletools/gallery/activities/MainActivity.kt

@@ -780,6 +780,14 @@ class MainActivity : SimpleActivity(), DirectoryOperationsListener {
             checkPlaceholderVisibility(dirs)
         }
         checkInvalidDirectories(dirs, directoryDao)
+
+        val everShownFolders = config.everShownFolders as HashSet
+        dirs.mapTo(everShownFolders) { it.path }
+
+        try {
+            config.everShownFolders = everShownFolders
+        } catch (ignored: Exception) {
+        }
     }
 
     private fun checkPlaceholderVisibility(dirs: ArrayList<Directory>) {

app/src/main/kotlin/com/simplemobiletools/gallery/helpers/Config.kt

@@ -364,4 +364,9 @@ class Config(context: Context) : BaseConfig(context) {
     var visibleBottomActions: Int
         get() = prefs.getInt(VISIBLE_BOTTOM_ACTIONS, DEFAULT_BOTTOM_ACTIONS)
         set(visibleBottomActions) = prefs.edit().putInt(VISIBLE_BOTTOM_ACTIONS, visibleBottomActions).apply()
+
+    // if a user hides a folder, then enables temporary hidden folder displaying, make sure we show it properly
+    var everShownFolders: Set<String>
+        get() = prefs.getStringSet(EVER_SHOWN_FOLDERS, HashSet<String>())
+        set(everShownFolders) = prefs.edit().putStringSet(EVER_SHOWN_FOLDERS, everShownFolders).apply()
 }

app/src/main/kotlin/com/simplemobiletools/gallery/helpers/Constants.kt

@@ -57,6 +57,7 @@ const val WERE_FAVORITES_PINNED = "were_favorites_pinned"
 const val WAS_RECYCLE_BIN_PINNED = "was_recycle_bin_pinned"
 const val USE_RECYCLE_BIN = "use_recycle_bin"
 const val GROUP_BY = "group_by"
+const val EVER_SHOWN_FOLDERS = "ever_shown_folders"
 
 // slideshow
 const val SLIDESHOW_INTERVAL = "slideshow_interval"

app/src/main/kotlin/com/simplemobiletools/gallery/helpers/MediaFetcher.kt

@@ -114,7 +114,7 @@ class MediaFetcher(val context: Context) {
         val foldersToIgnore = arrayListOf("/storage/emulated/legacy")
         val config = context.config
         val includedFolders = config.includedFolders
-        var foldersToScan = ArrayList<String>()
+        var foldersToScan = config.everShownFolders.toList() as ArrayList
 
         cursor.use {
             if (cursor.moveToFirst()) {