From 675aa0cb88850f7cdd9d44ced089c9bbb4f6ab97 Mon Sep 17 00:00:00 2001
From: kunfei <gekunfei@live.com>
Date: Fri, 7 Feb 2020 10:12:47 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BC=98=E5=8C=96?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../io/legado/app/help/ToTopListUpCallback.kt | 34 +++++++++++++++++++
 .../ui/main/bookshelf/books/BooksFragment.kt  |  6 +++-
 2 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 app/src/main/java/io/legado/app/help/ToTopListUpCallback.kt

diff --git a/app/src/main/java/io/legado/app/help/ToTopListUpCallback.kt b/app/src/main/java/io/legado/app/help/ToTopListUpCallback.kt
new file mode 100644
index 000000000..6fdef3dca
--- /dev/null
+++ b/app/src/main/java/io/legado/app/help/ToTopListUpCallback.kt
@@ -0,0 +1,34 @@
+package io.legado.app.help
+
+import androidx.recyclerview.widget.ListUpdateCallback
+import androidx.recyclerview.widget.RecyclerView
+import io.legado.app.base.adapter.ItemViewHolder
+
+class ToTopListUpCallback : ListUpdateCallback {
+    var firstInsert = -1
+    lateinit var adapter: RecyclerView.Adapter<ItemViewHolder>
+
+    override fun onChanged(position: Int, count: Int, payload: Any?) {
+        adapter.notifyItemRangeChanged(position, count, payload)
+    }
+
+    override fun onMoved(fromPosition: Int, toPosition: Int) {
+        if (toPosition == 0) {
+            firstInsert = 0
+        }
+        adapter.notifyItemMoved(fromPosition, toPosition)
+    }
+
+    override fun onInserted(position: Int, count: Int) {
+        if (firstInsert == -1 || firstInsert > position) {
+            firstInsert = position
+        }
+        adapter.notifyItemRangeInserted(position, count)
+    }
+
+    override fun onRemoved(position: Int, count: Int) {
+        adapter.notifyItemRangeRemoved(position, count)
+    }
+
+
+}
\ No newline at end of file
diff --git a/app/src/main/java/io/legado/app/ui/main/bookshelf/books/BooksFragment.kt b/app/src/main/java/io/legado/app/ui/main/bookshelf/books/BooksFragment.kt
index d7ffd7a34..496792c62 100644
--- a/app/src/main/java/io/legado/app/ui/main/bookshelf/books/BooksFragment.kt
+++ b/app/src/main/java/io/legado/app/ui/main/bookshelf/books/BooksFragment.kt
@@ -15,6 +15,7 @@ import io.legado.app.constant.EventBus
 import io.legado.app.constant.PreferKey
 import io.legado.app.data.entities.Book
 import io.legado.app.help.IntentDataHelp
+import io.legado.app.help.ToTopListUpCallback
 import io.legado.app.lib.theme.ATH
 import io.legado.app.lib.theme.accentColor
 import io.legado.app.ui.audio.AudioPlayActivity
@@ -88,6 +89,8 @@ class BooksFragment : BaseFragment(R.layout.fragment_books),
             else -> App.db.bookDao().observeByGroup(groupId)
         }
         bookshelfLiveData?.observe(this, Observer {
+            val listUpCallback = ToTopListUpCallback()
+            listUpCallback.adapter = booksAdapter
             val diffResult =
                 DiffUtil.calculateDiff(
                     BooksDiffCallBack(
@@ -96,7 +99,8 @@ class BooksFragment : BaseFragment(R.layout.fragment_books),
                     )
                 )
             booksAdapter.setItems(it, false)
-            diffResult.dispatchUpdatesTo(booksAdapter)
+            diffResult.dispatchUpdatesTo(listUpCallback)
+            rv_bookshelf.scrollToPosition(listUpCallback.firstInsert)
         })
     }