rewrite scrolling to improve performance

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

@@ -402,12 +402,16 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
     }
 
     private fun increaseColumnCount() {
+        directories_vertical_fastscroller.measureRecyclerViewOnRedraw()
+        directories_horizontal_fastscroller.measureRecyclerViewOnRedraw()
         config.dirColumnCnt = ++(directories_grid.layoutManager as GridLayoutManager).spanCount
         invalidateOptionsMenu()
         directories_grid.adapter?.notifyDataSetChanged()
     }
 
     private fun reduceColumnCount() {
+        directories_vertical_fastscroller.measureRecyclerViewOnRedraw()
+        directories_horizontal_fastscroller.measureRecyclerViewOnRedraw()
         config.dirColumnCnt = --(directories_grid.layoutManager as GridLayoutManager).spanCount
         invalidateOptionsMenu()
         directories_grid.adapter?.notifyDataSetChanged()
@@ -533,6 +537,11 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
 
         directories_empty_text_label.beVisibleIf(dirs.isEmpty() && !isFromCache)
         directories_empty_text.beVisibleIf(dirs.isEmpty() && !isFromCache)
+        directories_grid.beVisibleIf(directories_empty_text_label.isGone())
+
+        val allowHorizontalScroll = config.scrollHorizontally && config.viewTypeFiles == VIEW_TYPE_GRID
+        directories_vertical_fastscroller.beVisibleIf(directories_grid.isVisible() && !allowHorizontalScroll)
+        directories_horizontal_fastscroller.beVisibleIf(directories_grid.isVisible() && allowHorizontalScroll)
 
         checkLastMediaChanged()
         if (dirs.hashCode() == mDirs.hashCode()) {
@@ -559,7 +568,8 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
         val currAdapter = directories_grid.adapter
         if (currAdapter == null) {
             initZoomListener()
-            DirectoryAdapter(this, mDirs, this, directories_grid, isPickIntent(intent) || isGetAnyContentIntent(intent)) {
+            val fastscroller = if (config.scrollHorizontally) directories_horizontal_fastscroller else directories_vertical_fastscroller
+            DirectoryAdapter(this, mDirs, this, directories_grid, isPickIntent(intent) || isGetAnyContentIntent(intent), fastscroller) {
                 itemClicked((it as Directory).path)
             }.apply {
                 setupZoomListener(mZoomListener)

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

@@ -182,7 +182,8 @@ class MediaActivity : SimpleActivity(), MediaAdapter.MediaOperationsListener {
         val currAdapter = media_grid.adapter
         if (currAdapter == null) {
             initZoomListener()
-            MediaAdapter(this, mMedia, this, mIsGetImageIntent || mIsGetVideoIntent || mIsGetAnyIntent, mAllowPickingMultiple, media_grid) {
+            val fastscroller = if (config.scrollHorizontally) media_horizontal_fastscroller else media_vertical_fastscroller
+            MediaAdapter(this, mMedia, this, mIsGetImageIntent || mIsGetVideoIntent || mIsGetAnyIntent, mAllowPickingMultiple, media_grid, fastscroller) {
                 itemClicked((it as Medium).path)
             }.apply {
                 setupZoomListener(mZoomListener)
@@ -466,12 +467,16 @@ class MediaActivity : SimpleActivity(), MediaAdapter.MediaOperationsListener {
     }
 
     private fun increaseColumnCount() {
+        media_vertical_fastscroller.measureRecyclerViewOnRedraw()
+        media_horizontal_fastscroller.measureRecyclerViewOnRedraw()
         config.mediaColumnCnt = ++(media_grid.layoutManager as GridLayoutManager).spanCount
         invalidateOptionsMenu()
         media_grid.adapter?.notifyDataSetChanged()
     }
 
     private fun reduceColumnCount() {
+        media_vertical_fastscroller.measureRecyclerViewOnRedraw()
+        media_horizontal_fastscroller.measureRecyclerViewOnRedraw()
         config.mediaColumnCnt = --(media_grid.layoutManager as GridLayoutManager).spanCount
         invalidateOptionsMenu()
         media_grid.adapter?.notifyDataSetChanged()
@@ -548,6 +553,11 @@ class MediaActivity : SimpleActivity(), MediaAdapter.MediaOperationsListener {
 
         media_empty_text_label.beVisibleIf(media.isEmpty() && !isFromCache)
         media_empty_text.beVisibleIf(media.isEmpty() && !isFromCache)
+        media_grid.beVisibleIf(media_empty_text_label.isGone())
+
+        val allowHorizontalScroll = config.scrollHorizontally && config.viewTypeFiles == VIEW_TYPE_GRID
+        media_vertical_fastscroller.beVisibleIf(media_grid.isVisible() && !allowHorizontalScroll)
+        media_horizontal_fastscroller.beVisibleIf(media_grid.isVisible() && allowHorizontalScroll)
 
         checkLastMediaChanged()
         if (mLastDrawnHashCode == 0)

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

@@ -11,6 +11,7 @@ import com.simplemobiletools.commons.dialogs.ConfirmationDialog
 import com.simplemobiletools.commons.dialogs.PropertiesDialog
 import com.simplemobiletools.commons.dialogs.RenameItemDialog
 import com.simplemobiletools.commons.extensions.*
+import com.simplemobiletools.commons.views.FastScroller
 import com.simplemobiletools.commons.views.MyRecyclerView
 import com.simplemobiletools.gallery.R
 import com.simplemobiletools.gallery.dialogs.ExcludeFolderDialog
@@ -24,7 +25,8 @@ import java.io.File
 import java.util.*
 
 class DirectoryAdapter(activity: BaseSimpleActivity, var dirs: MutableList<Directory>, val listener: DirOperationsListener?, recyclerView: MyRecyclerView,
-                       val isPickIntent: Boolean, itemClick: (Any) -> Unit) : MyRecyclerViewAdapter(activity, recyclerView, itemClick) {
+                       val isPickIntent: Boolean, fastScroller: FastScroller? = null, itemClick: (Any) -> Unit) :
+        MyRecyclerViewAdapter(activity, recyclerView, fastScroller, itemClick) {
 
     private val config = activity.config
     private val isListViewType = config.viewTypeFolders == VIEW_TYPE_LIST

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

@@ -14,7 +14,7 @@ import kotlinx.android.synthetic.main.item_manage_folder.view.*
 import java.util.*
 
 class ManageFoldersAdapter(activity: BaseSimpleActivity, var folders: ArrayList<String>, val isShowingExcludedFolders: Boolean, val listener: RefreshRecyclerViewListener?,
-                           recyclerView: MyRecyclerView, itemClick: (Any) -> Unit) : MyRecyclerViewAdapter(activity, recyclerView, itemClick) {
+                           recyclerView: MyRecyclerView, itemClick: (Any) -> Unit) : MyRecyclerViewAdapter(activity, recyclerView, null, itemClick) {
 
     private val config = activity.config
 

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

@@ -16,7 +16,7 @@ import java.io.File
 import java.util.*
 
 class ManageHiddenFoldersAdapter(activity: BaseSimpleActivity, var folders: ArrayList<String>, val listener: RefreshRecyclerViewListener?,
-                                 recyclerView: MyRecyclerView, itemClick: (Any) -> Unit) : MyRecyclerViewAdapter(activity, recyclerView, itemClick) {
+                                 recyclerView: MyRecyclerView, itemClick: (Any) -> Unit) : MyRecyclerViewAdapter(activity, recyclerView, null, itemClick) {
 
     private val config = activity.config
 

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

@@ -1,6 +1,8 @@
 package com.simplemobiletools.gallery.adapters
 
 import android.net.Uri
+import android.os.Handler
+import android.os.Looper
 import android.view.Menu
 import android.view.View
 import android.view.ViewGroup
@@ -12,22 +14,26 @@ import com.simplemobiletools.commons.dialogs.RenameItemDialog
 import com.simplemobiletools.commons.extensions.applyColorFilter
 import com.simplemobiletools.commons.extensions.beVisibleIf
 import com.simplemobiletools.commons.extensions.isActivityDestroyed
+import com.simplemobiletools.commons.views.FastScroller
 import com.simplemobiletools.commons.views.MyRecyclerView
 import com.simplemobiletools.gallery.R
 import com.simplemobiletools.gallery.dialogs.DeleteWithRememberDialog
 import com.simplemobiletools.gallery.extensions.*
 import com.simplemobiletools.gallery.helpers.VIEW_TYPE_LIST
 import com.simplemobiletools.gallery.models.Medium
-import kotlinx.android.synthetic.main.photo_video_item_list.view.*
+import kotlinx.android.synthetic.main.photo_video_item_grid.view.*
 import java.io.File
 import java.util.*
 
 class MediaAdapter(activity: BaseSimpleActivity, var media: MutableList<Medium>, val listener: MediaOperationsListener?, val isAGetIntent: Boolean,
-                   val allowMultiplePicks: Boolean, recyclerView: MyRecyclerView, itemClick: (Any) -> Unit) : MyRecyclerViewAdapter(activity, recyclerView, itemClick) {
+                   val allowMultiplePicks: Boolean, recyclerView: MyRecyclerView, fastScroller: FastScroller? = null,
+                   itemClick: (Any) -> Unit) : MyRecyclerViewAdapter(activity, recyclerView, fastScroller, itemClick) {
 
     private val config = activity.config
     private val isListViewType = config.viewTypeFiles == VIEW_TYPE_LIST
     private var skipConfirmationDialog = false
+    private var visibleItemPaths = ArrayList<String>()
+    private var delayHandler = Handler(Looper.getMainLooper())
 
     private var scrollHorizontally = config.scrollHorizontally
     private var animateGifs = config.animateGifs
@@ -51,6 +57,7 @@ class MediaAdapter(activity: BaseSimpleActivity, var media: MutableList<Medium>,
 
     override fun onBindViewHolder(holder: MyRecyclerViewAdapter.ViewHolder, position: Int) {
         val medium = media[position]
+        visibleItemPaths.add(medium.path)
         val view = holder.bindView(medium, !allowMultiplePicks) { itemView, layoutPosition ->
             setupView(itemView, medium)
         }
@@ -92,7 +99,9 @@ class MediaAdapter(activity: BaseSimpleActivity, var media: MutableList<Medium>,
     override fun onViewRecycled(holder: ViewHolder?) {
         super.onViewRecycled(holder)
         if (!activity.isActivityDestroyed()) {
-            Glide.with(activity).clear(holder?.itemView?.medium_thumbnail)
+            val itemView = holder?.itemView
+            visibleItemPaths.remove(itemView?.photo_name?.tag)
+            Glide.with(activity).clear(itemView?.medium_thumbnail)
         }
     }
 
@@ -259,7 +268,15 @@ class MediaAdapter(activity: BaseSimpleActivity, var media: MutableList<Medium>,
             play_outline.beVisibleIf(medium.video)
             photo_name.beVisibleIf(displayFilenames || isListViewType)
             photo_name.text = medium.name
-            activity.loadImage(medium.path, medium_thumbnail, scrollHorizontally, animateGifs, cropThumbnails)
+            photo_name.tag = medium.path
+
+            medium_thumbnail.isHorizontalScrolling = scrollHorizontally
+            delayHandler.postDelayed({
+                val isVisible = visibleItemPaths.contains(medium.path)
+                if (isVisible) {
+                    activity.loadImage(medium.path, medium_thumbnail, scrollHorizontally, animateGifs, cropThumbnails)
+                }
+            }, 200)
 
             if (isListViewType) {
                 photo_name.setTextColor(textColor)