properly handle grid updating if a thumbnail gets deleted

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

@@ -46,6 +46,7 @@ import kotlinx.android.synthetic.main.activity_media.*
 import java.io.File
 import java.io.IOException
 import java.util.*
+import kotlin.collections.ArrayList
 
 class MediaActivity : SimpleActivity(), MediaOperationsListener {
     private val LAST_MEDIA_CHECK_PERIOD = 3000L
@@ -989,6 +990,22 @@ class MediaActivity : SimpleActivity(), MediaOperationsListener {
         finish()
     }
 
+    override fun updateMediaGridDecoration(media: ArrayList<ThumbnailItem>) {
+        var currentGridPosition = 0
+        media.forEach {
+            if (it is Medium) {
+                it.gridPosition = currentGridPosition++
+            } else if (it is ThumbnailSection) {
+                currentGridPosition = 0
+            }
+        }
+
+        if (media_grid.itemDecorationCount > 0) {
+            val currentGridDecoration = media_grid.getItemDecorationAt(0) as GridSpacingItemDecoration
+            currentGridDecoration.items = media
+        }
+    }
+
     private fun setAsDefaultFolder() {
         config.defaultFolder = mPath
         invalidateOptionsMenu()

app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/SearchActivity.kt

@@ -379,4 +379,7 @@ class SearchActivity : SimpleActivity(), MediaOperationsListener {
 
     override fun selectedPaths(paths: ArrayList<String>) {
     }
+
+    override fun updateMediaGridDecoration(media: ArrayList<ThumbnailItem>) {
+    }
 }

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

@@ -439,6 +439,7 @@ class MediaAdapter(activity: BaseSimpleActivity, var media: ArrayList<ThumbnailI
 
             media.removeAll(removeMedia)
             listener?.tryDeleteFiles(fileDirItems)
+            listener?.updateMediaGridDecoration(media)
             removeSelectedItems(positions)
             currentMediaHash = media.hashCode()
         }

app/src/main/kotlin/com/simplemobiletools/gallery/pro/interfaces/MediaOperationsListener.kt

@@ -1,6 +1,7 @@
 package com.simplemobiletools.gallery.pro.interfaces
 
 import com.simplemobiletools.commons.models.FileDirItem
+import com.simplemobiletools.gallery.pro.models.ThumbnailItem
 
 interface MediaOperationsListener {
     fun refreshItems()
@@ -8,4 +9,6 @@ interface MediaOperationsListener {
     fun tryDeleteFiles(fileDirItems: ArrayList<FileDirItem>)
 
     fun selectedPaths(paths: ArrayList<String>)
+
+    fun updateMediaGridDecoration(media: ArrayList<ThumbnailItem>)
 }