cache the directories to show instantly

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

@@ -14,6 +14,8 @@ import android.support.v7.widget.GridLayoutManager
 import android.view.Menu
 import android.view.MenuItem
 import android.view.View
+import com.google.gson.Gson
+import com.google.gson.reflect.TypeToken
 import com.simplemobiletools.commons.extensions.*
 import com.simplemobiletools.commons.models.Release
 import com.simplemobiletools.gallery.BuildConfig
@@ -97,6 +99,7 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
     override fun onPause() {
         super.onPause()
         deleteDirs()
+        storeDirectories()
     }
 
     override fun onDestroy() {
@@ -135,6 +138,10 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
         if (mIsGettingDirs)
             return
 
+        val token = object : TypeToken<List<Directory>>() {}.type
+        val dirs = Gson().fromJson<ArrayList<Directory>>(config.directories, token) ?: ArrayList<Directory>(1)
+        gotDirectories(dirs)
+
         mIsGettingDirs = true
         GetDirectoriesAsynctask(applicationContext, mIsPickVideoIntent || mIsGetVideoContentIntent, mIsPickImageIntent || mIsGetImageContentIntent, mToBeDeleted) {
             gotDirectories(it)
@@ -329,6 +336,12 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
         mDirs = dirs
 
         setupAdapter()
+        storeDirectories()
+    }
+
+    fun storeDirectories() {
+        val directories = Gson().toJson(mDirs)
+        config.directories = directories
     }
 
     private fun setupAdapter() {

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

@@ -95,4 +95,8 @@ class Config(context: Context) : BaseConfig(context) {
     var mediaColumnCnt: Int
         get() = prefs.getInt(MEDIA_COLUMN_CNT, context.resources.getInteger(R.integer.media_columns))
         set(mediaColumnCnt) = prefs.edit().putInt(MEDIA_COLUMN_CNT, mediaColumnCnt).apply()
+
+    var directories: String
+        get() = prefs.getString(DIRECTORIES, "")
+        set(directories) = prefs.edit().putString(DIRECTORIES, directories).apply()
 }

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

@@ -1,7 +1,6 @@
 package com.simplemobiletools.gallery.helpers
 
 // shared preferences
-val PREFS_KEY = "Gallery"
 val IS_SAME_SORTING = "is_same_sorting"
 val SORT_ORDER = "sort_order"
 val DIRECTORY_SORT_ORDER = "directory_sort_order"
@@ -23,13 +22,13 @@ val SORT_BY_SIZE = 4
 val SORT_BY_DATE_TAKEN = 8
 val SORT_DESCENDING = 1024
 
-
 val DIRECTORY = "directory"
 val MEDIUM = "medium"
 val GET_IMAGE_INTENT = "get_image_intent"
 val GET_VIDEO_INTENT = "get_video_intent"
 val GET_ANY_INTENT = "get_any_intent"
 val SET_WALLPAPER_INTENT = "set_wallpaper_intent"
+val DIRECTORIES = "directories"
 
 val REQUEST_EDIT_IMAGE = 1
 val REQUEST_SET_WALLPAPER = 2

app/src/main/kotlin/com/simplemobiletools/gallery/models/Directory.kt

@@ -4,10 +4,12 @@ import com.simplemobiletools.gallery.helpers.SORT_BY_DATE_MODIFIED
 import com.simplemobiletools.gallery.helpers.SORT_BY_NAME
 import com.simplemobiletools.gallery.helpers.SORT_BY_SIZE
 import com.simplemobiletools.gallery.helpers.SORT_DESCENDING
+import java.io.Serializable
 
 data class Directory(val path: String, val thumbnail: String, val name: String, var mediaCnt: Int, val date_modified: Long, val date_taken: Long,
-                var size: Long) : Comparable<Directory> {
+                var size: Long) : Serializable, Comparable<Directory> {
     companion object {
+        private val serialVersionUID = -6553649863575455L
         var sorting: Int = 0
     }