implement custom sorting per folder

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

@@ -145,7 +145,7 @@ class MediaActivity : SimpleActivity(), MediaAdapter.MediaOperationsListener {
     }
 
     private fun showSortingDialog() {
-        ChangeSortingDialog(this, false, true) {
+        ChangeSortingDialog(this, false, true, mPath) {
             getMedia()
         }
     }

app/src/main/kotlin/com/simplemobiletools/gallery/asynctasks/GetMediaAsynctask.kt

@@ -25,7 +25,7 @@ class GetMediaAsynctask(val context: Context, val mPath: String, val isPickVideo
     override fun onPreExecute() {
         super.onPreExecute()
         showMedia = config.showMedia
-        fileSorting = config.fileSorting
+        fileSorting = config.getFileSorting(mPath)
     }
 
     override fun doInBackground(vararg params: Void): ArrayList<Medium> {

app/src/main/kotlin/com/simplemobiletools/gallery/dialogs/ChangeSortingDialog.kt

@@ -12,7 +12,8 @@ import com.simplemobiletools.gallery.extensions.config
 import com.simplemobiletools.gallery.helpers.*
 import kotlinx.android.synthetic.main.dialog_change_sorting.view.*
 
-class ChangeSortingDialog(val activity: SimpleActivity, val isDirectorySorting: Boolean, val showFolderCheckbox: Boolean, val callback: () -> Unit) :
+class ChangeSortingDialog(val activity: SimpleActivity, val isDirectorySorting: Boolean, showFolderCheckbox: Boolean,
+                          val path: String = "", val callback: () -> Unit) :
         DialogInterface.OnClickListener {
     companion object {
         private var currSorting = 0
@@ -26,6 +27,7 @@ class ChangeSortingDialog(val activity: SimpleActivity, val isDirectorySorting:
         view = LayoutInflater.from(activity).inflate(R.layout.dialog_change_sorting, null)
         view.use_for_this_folder_divider.beVisibleIf(showFolderCheckbox)
         view.sorting_dialog_use_for_this_folder.beVisibleIf(showFolderCheckbox)
+        view.sorting_dialog_use_for_this_folder.isChecked = config.hasCustomSorting(path)
 
         AlertDialog.Builder(activity)
                 .setPositiveButton(R.string.ok, this)
@@ -34,7 +36,7 @@ class ChangeSortingDialog(val activity: SimpleActivity, val isDirectorySorting:
             activity.setupDialogStuff(view, this, R.string.sort_by)
         }
 
-        currSorting = if (isDirectorySorting) config.directorySorting else config.fileSorting
+        currSorting = if (isDirectorySorting) config.directorySorting else config.getFileSorting(path)
         setupSortRadio()
         setupOrderRadio()
     }
@@ -78,7 +80,12 @@ class ChangeSortingDialog(val activity: SimpleActivity, val isDirectorySorting:
         if (isDirectorySorting) {
             config.directorySorting = sorting
         } else {
-            config.fileSorting = sorting
+            if (view.sorting_dialog_use_for_this_folder.isChecked) {
+                config.saveFileSorting(path, sorting)
+            } else {
+                config.removeFileSorting(path)
+                config.fileSorting = sorting
+            }
         }
         callback.invoke()
     }

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

@@ -18,6 +18,22 @@ class Config(context: Context) : BaseConfig(context) {
         get() = prefs.getInt(DIRECTORY_SORT_ORDER, SORT_BY_DATE_MODIFIED or SORT_DESCENDING)
         set(order) = prefs.edit().putInt(DIRECTORY_SORT_ORDER, order).apply()
 
+    fun saveFileSorting(path: String, value: Int) {
+        if (path.isEmpty()) {
+            fileSorting = value
+        } else {
+            prefs.edit().putInt(SORT_FOLDER_PREFIX + path, value).apply()
+        }
+    }
+
+    fun getFileSorting(path: String) = prefs.getInt(SORT_FOLDER_PREFIX + path, fileSorting)
+
+    fun removeFileSorting(path: String) {
+        prefs.edit().remove(SORT_FOLDER_PREFIX + path).apply()
+    }
+
+    fun hasCustomSorting(path: String) = prefs.contains(SORT_FOLDER_PREFIX + path)
+
     var wasHideFolderTooltipShown: Boolean
         get() = prefs.getBoolean(HIDE_FOLDER_TOOLTIP_SHOWN, false)
         set(wasShown) = prefs.edit().putBoolean(HIDE_FOLDER_TOOLTIP_SHOWN, wasShown).apply()

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

@@ -3,6 +3,7 @@ package com.simplemobiletools.gallery.helpers
 // shared preferences
 val SORT_ORDER = "sort_order"
 val DIRECTORY_SORT_ORDER = "directory_sort_order"
+val SORT_FOLDER_PREFIX = "sort_folder_"
 val SHOW_HIDDEN_FOLDERS = "show_hidden_folders"
 val AUTOPLAY_VIDEOS = "autoplay_videos"
 val LOOP_VIDEOS = "loop_videos"