diff --git a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/MainActivity.kt b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/MainActivity.kt
index fad2c47b8..0d91caba2 100644
--- a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/MainActivity.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/MainActivity.kt
@@ -294,7 +294,7 @@ class MainActivity : SimpleActivity(), DirectoryOperationsListener {
             if (mCurrentPathPrefix.isEmpty()) {
                 super.onBackPressed()
             } else {
-                mOpenedSubfolders.removeAt(mOpenedSubfolders.size - 1)
+                mOpenedSubfolders.removeLast()
                 mCurrentPathPrefix = mOpenedSubfolders.last()
                 setupAdapter(mDirs)
             }
diff --git a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/ViewPagerActivity.kt b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/ViewPagerActivity.kt
index a9d1df0fa..81c108f08 100644
--- a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/ViewPagerActivity.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/ViewPagerActivity.kt
@@ -1279,7 +1279,7 @@ class ViewPagerActivity : SimpleActivity(), ViewPager.OnPageChangeListener, View
         if (refetchViewPagerPosition || mPos == -1) {
             mPos = getPositionInList(media)
             if (mPos == -1) {
-                min(mPos, media.size - 1)
+                min(mPos, media.lastIndex)
             }
         }
 
@@ -1384,7 +1384,7 @@ class ViewPagerActivity : SimpleActivity(), ViewPager.OnPageChangeListener, View
                 putExtra(IS_FROM_GALLERY, true)
                 putExtra(REAL_FILE_PATH, path)
                 putExtra(SHOW_PREV_ITEM, view_pager.currentItem != 0)
-                putExtra(SHOW_NEXT_ITEM, view_pager.currentItem != mMediaFiles.size - 1)
+                putExtra(SHOW_NEXT_ITEM, view_pager.currentItem != mMediaFiles.lastIndex)
 
                 try {
                     startActivityForResult(this, REQUEST_VIEW_VIDEO)
@@ -1439,7 +1439,7 @@ class ViewPagerActivity : SimpleActivity(), ViewPager.OnPageChangeListener, View
         return if (getCurrentMedia().isEmpty() || mPos == -1) {
             null
         } else {
-            getCurrentMedia()[min(mPos, getCurrentMedia().size - 1)]
+            getCurrentMedia()[min(mPos, getCurrentMedia().lastIndex)]
         }
     }
 
diff --git a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/adapters/PortraitPhotosAdapter.kt b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/adapters/PortraitPhotosAdapter.kt
index 1752db8ca..6154e6df6 100644
--- a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/adapters/PortraitPhotosAdapter.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/adapters/PortraitPhotosAdapter.kt
@@ -13,10 +13,9 @@ import com.bumptech.glide.signature.ObjectKey
 import com.simplemobiletools.commons.extensions.getFileKey
 import com.simplemobiletools.gallery.pro.R
 import kotlinx.android.synthetic.main.portrait_photo_item.view.*
-import java.util.*
 
 class PortraitPhotosAdapter(val context: Context, val photos: ArrayList<String>, val sideElementWidth: Int, val itemClick: (Int, Int) -> Unit) :
-        RecyclerView.Adapter<PortraitPhotosAdapter.ViewHolder>() {
+    RecyclerView.Adapter<PortraitPhotosAdapter.ViewHolder>() {
 
     var currentSelectionIndex = -1
     var views = HashMap<Int, View>()
@@ -48,7 +47,7 @@ class PortraitPhotosAdapter(val context: Context, val photos: ArrayList<String>,
     inner class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
         fun bindView(photo: String, position: Int): View {
             itemView.apply {
-                portrait_photo_item_thumbnail.layoutParams.width = if (position == 0 || position == photos.size - 1) {
+                portrait_photo_item_thumbnail.layoutParams.width = if (position == 0 || position == photos.lastIndex) {
                     sideElementWidth
                 } else {
                     itemWidth
@@ -61,15 +60,15 @@ class PortraitPhotosAdapter(val context: Context, val photos: ArrayList<String>,
                 }
 
                 val options = RequestOptions()
-                        .signature(ObjectKey(photo.getFileKey()))
-                        .diskCacheStrategy(DiskCacheStrategy.RESOURCE)
-                        .centerCrop()
+                    .signature(ObjectKey(photo.getFileKey()))
+                    .diskCacheStrategy(DiskCacheStrategy.RESOURCE)
+                    .centerCrop()
 
                 Glide.with(context)
-                        .load(photo)
-                        .transition(DrawableTransitionOptions.withCrossFade())
-                        .apply(options)
-                        .into(portrait_photo_item_thumbnail)
+                    .load(photo)
+                    .transition(DrawableTransitionOptions.withCrossFade())
+                    .apply(options)
+                    .into(portrait_photo_item_thumbnail)
 
                 if (photo.isNotEmpty()) {
                     isClickable = true
diff --git a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/dialogs/PickDirectoryDialog.kt b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/dialogs/PickDirectoryDialog.kt
index 768567c7b..30424e724 100644
--- a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/dialogs/PickDirectoryDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/dialogs/PickDirectoryDialog.kt
@@ -147,7 +147,7 @@ class PickDirectoryDialog(
             if (currentPathPrefix.isEmpty()) {
                 dialog?.dismiss()
             } else {
-                openedSubfolders.removeAt(openedSubfolders.size - 1)
+                openedSubfolders.removeLast()
                 currentPathPrefix = openedSubfolders.last()
                 gotDirectories(allDirectories)
             }
diff --git a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/jobs/NewPhotoFetcher.kt b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/jobs/NewPhotoFetcher.kt
index ad5ada9f7..ad91c0d96 100644
--- a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/jobs/NewPhotoFetcher.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/jobs/NewPhotoFetcher.kt
@@ -70,7 +70,7 @@ class NewPhotoFetcher : JobService() {
                 for (uri in params.triggeredContentUris!!) {
                     val path = uri.pathSegments
                     if (path != null && (path.size == PHOTO_PATH_SEGMENTS.size + 1 || path.size == VIDEO_PATH_SEGMENTS.size + 1)) {
-                        ids.add(path[path.size - 1])
+                        ids.add(path[path.lastIndex])
                     }
                 }