The orientation parameter of LinearLayoutManager::setOrientation should be @RecyclerView.Orientation

src/main/java/com/kdanmobile/reader/screen/view/BookmarkView.kt

@@ -36,7 +36,7 @@ class BookmarkView: RelativeLayout, LeftToolbarView {
     private fun initView() {
         LayoutInflater.from(context).inflate(R.layout.view_bookmark, this)
         val layoutManager = LinearLayoutManager(context)
-        layoutManager.orientation = LinearLayoutManager.VERTICAL
+        layoutManager.orientation = RecyclerView.VERTICAL
 
         id_km_bookmark_recycler.setHasFixedSize(true)
         id_km_bookmark_recycler.layoutManager = layoutManager

src/main/java/com/kdanmobile/reader/screen/view/ThumbnailView.kt

@@ -33,7 +33,7 @@ class ThumbnailView: RelativeLayout, LeftToolbarView {
     private fun initView() {
         LayoutInflater.from(context).inflate(R.layout.view_thumbnail, this)
         val layoutManager = LinearLayoutManager(context)
-        layoutManager.orientation = LinearLayoutManager.VERTICAL
+        layoutManager.orientation = RecyclerView.VERTICAL
 
         id_km_thumb_recycler.setHasFixedSize(true)
         id_km_thumb_recycler.layoutManager = layoutManager