add the file renaming functionality itself

app/src/main/kotlin/com/simplemobiletools/gallery/adapters/DirectoryAdapter.kt

@@ -174,19 +174,18 @@ class DirectoryAdapter(val activity: SimpleActivity, val dirs: MutableList<Direc
     }
 
     private fun toggleFoldersVisibility(hide: Boolean) {
-        val paths = getSelectedPaths()
+        getSelectedPaths().forEach {
-        for (path in paths) {
             if (hide) {
                 if (config.wasHideFolderTooltipShown) {
-                    hideFolder(path)
+                    hideFolder(it)
                 } else {
                     config.wasHideFolderTooltipShown = true
                     ConfirmationDialog(activity, activity.getString(R.string.hide_folder_description)) {
-                        hideFolder(path)
+                        hideFolder(it)
                     }
                 }
             } else {
-                activity.removeNoMedia(path) {
+                activity.removeNoMedia(it) {
                     noMediaHandled()
                 }
             }

app/src/main/kotlin/com/simplemobiletools/gallery/adapters/MediaAdapter.kt

@@ -13,6 +13,7 @@ import com.simplemobiletools.commons.dialogs.ConfirmationDialog
 import com.simplemobiletools.commons.dialogs.PropertiesDialog
 import com.simplemobiletools.commons.dialogs.RenameItemDialog
 import com.simplemobiletools.commons.extensions.beVisibleIf
+import com.simplemobiletools.commons.extensions.renameFile
 import com.simplemobiletools.gallery.R
 import com.simplemobiletools.gallery.activities.SimpleActivity
 import com.simplemobiletools.gallery.extensions.*
@@ -149,7 +150,26 @@ class MediaAdapter(val activity: SimpleActivity, var media: MutableList<Medium>,
     }
 
     private fun toggleFileVisibility(hide: Boolean) {
-
+        Thread({
+            getSelectedMedia().forEach {
+                val oldFile = File(it.path)
+                val path = oldFile.parent
+                var filename = it.name
+                if (hide) {
+                    filename = ".${filename.trimStart('.')}"
+                } else {
+                    filename = filename.substring(1, filename.length)
+                }
+                val newFile = File(path, filename)
+                activity.renameFile(oldFile, newFile) {
+                    newFile.setLastModified(System.currentTimeMillis())
+                }
+            }
+            activity.runOnUiThread {
+                listener?.refreshItems()
+                actMode?.finish()
+            }
+        }).start()
     }
 
     private fun shareMedia() {