recreate whole thumbnails view on toggling horizontal scroll

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

@@ -138,8 +138,9 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
         }
 
         if (mStoredScrollHorizontally != config.scrollHorizontally) {
-            getRecyclerAdapter()?.updateScrollHorizontally(config.viewTypeFolders != VIEW_TYPE_LIST && config.scrollHorizontally)
+            mLoadedInitialPhotos = false
-            setupScrollDirection()
+            directories_grid.adapter = null
+            getDirectories()
         }
 
         if (mStoredTextColor != config.textColor) {
@@ -382,6 +383,7 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
     private fun toggleTemporarilyShowHidden(show: Boolean) {
         mLoadedInitialPhotos = false
         config.temporarilyShowHidden = show
+        directories_grid.adapter = null
         getDirectories()
         invalidateOptionsMenu()
     }

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

@@ -61,8 +61,6 @@ class MediaActivity : SimpleActivity(), MediaAdapter.MediaOperationsListener {
     private var mIsSearchOpen = false
     private var mLatestMediaId = 0L
     private var mLatestMediaDateId = 0L
-    private var mSectionTitleHeight = 0
-    private var mThumbnailHeight = 0
     private var mLastMediaHandler = Handler()
     private var mTempShowHiddenHandler = Handler()
     private var mCurrAsyncTask: GetMediaAsynctask? = null
@@ -126,8 +124,9 @@ class MediaActivity : SimpleActivity(), MediaAdapter.MediaOperationsListener {
         }
 
         if (mStoredScrollHorizontally != config.scrollHorizontally) {
-            getMediaAdapter()?.updateScrollHorizontally(config.viewTypeFiles != VIEW_TYPE_LIST || !config.scrollHorizontally)
+            mLoadedInitialPhotos = false
-            setupScrollDirection()
+            media_grid.adapter = null
+            getMedia()
         }
 
         if (mStoredTextColor != config.textColor) {
@@ -591,11 +590,29 @@ class MediaActivity : SimpleActivity(), MediaAdapter.MediaOperationsListener {
     }
 
     private fun measureRecyclerViewContent(media: ArrayList<ThumbnailItem>) {
-        val layoutManager = media_grid.layoutManager as MyGridLayoutManager
         media_grid.onGlobalLayout {
-            val hasSections = config.getFolderGrouping(mPath) and GROUP_BY_NONE == 0
+            if (config.scrollHorizontally) {
-            mSectionTitleHeight = if (hasSections) layoutManager.getChildAt(0)?.height ?: 0 else 0
+                calculateContentWidth(media)
-            mThumbnailHeight = if (hasSections) layoutManager.getChildAt(1)?.height ?: 0 else layoutManager.getChildAt(0)?.height ?: 0
+            } else {
+                calculateContentHeight(media)
+            }
+        }
+    }
+
+    private fun calculateContentWidth(media: ArrayList<ThumbnailItem>) {
+        val layoutManager = media_grid.layoutManager as MyGridLayoutManager
+        val mThumbnailWidth = layoutManager.getChildAt(0)?.width ?: 0
+        val fullWidth = ((media.size - 1) / layoutManager.spanCount + 1) * mThumbnailWidth
+        media_horizontal_fastscroller.setContentWidth(fullWidth)
+        media_horizontal_fastscroller.setScrollTo(media_grid.computeHorizontalScrollOffset())
+    }
+
+    private fun calculateContentHeight(media: ArrayList<ThumbnailItem>) {
+        val layoutManager = media_grid.layoutManager as MyGridLayoutManager
+        val hasSections = config.getFolderGrouping(mPath) and GROUP_BY_NONE == 0 && !config.scrollHorizontally
+        val mSectionTitleHeight = if (hasSections) layoutManager.getChildAt(0)?.height ?: 0 else 0
+        val mThumbnailHeight = if (hasSections) layoutManager.getChildAt(1)?.height ?: 0 else layoutManager.getChildAt(0)?.height
+                ?: 0
 
         var fullHeight = 0
         var curSectionItems = 0
@@ -616,7 +633,6 @@ class MediaActivity : SimpleActivity(), MediaAdapter.MediaOperationsListener {
         media_vertical_fastscroller.setContentHeight(fullHeight)
         media_vertical_fastscroller.setScrollTo(media_grid.computeVerticalScrollOffset())
     }
-    }
 
     private fun initZoomListener() {
         if (config.viewTypeFiles == VIEW_TYPE_GRID) {

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

@@ -442,11 +442,6 @@ class DirectoryAdapter(activity: BaseSimpleActivity, var dirs: ArrayList<Directo
         notifyDataSetChanged()
     }
 
-    fun updateScrollHorizontally(scrollHorizontally: Boolean) {
-        this.scrollHorizontally = scrollHorizontally
-        notifyDataSetChanged()
-    }
-
     private fun setupView(view: View, directory: Directory) {
         view.apply {
             dir_name.text = directory.name

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

@@ -335,7 +335,6 @@ class MediaAdapter(activity: BaseSimpleActivity, var media: MutableList<Thumbnai
                 enableInstantLoad()
                 notifyDataSetChanged()
                 finishActMode()
-                fastScroller?.measureRecyclerView()
             }, 100L)
         }
     }
@@ -356,11 +355,6 @@ class MediaAdapter(activity: BaseSimpleActivity, var media: MutableList<Thumbnai
         notifyDataSetChanged()
     }
 
-    fun updateScrollHorizontally(scrollHorizontally: Boolean) {
-        this.scrollHorizontally = scrollHorizontally
-        notifyDataSetChanged()
-    }
-
     private fun enableInstantLoad() {
         loadImageInstantly = true
         delayHandler.postDelayed({