feat: 优化

app/src/main/java/io/legado/app/ui/main/bookshelf/books/BooksFragment.kt

@@ -7,6 +7,7 @@ import androidx.lifecycle.Observer
 import androidx.recyclerview.widget.DiffUtil
 import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
 import io.legado.app.App
 import io.legado.app.R
 import io.legado.app.base.BaseFragment
@@ -27,6 +28,7 @@ import io.legado.app.utils.getViewModelOfActivity
 import io.legado.app.utils.observeEvent
 import kotlinx.android.synthetic.main.fragment_books.*
 import org.jetbrains.anko.startActivity
+import kotlin.math.max
 
 
 class BooksFragment : BaseFragment(R.layout.fragment_books),
@@ -75,6 +77,23 @@ class BooksFragment : BaseFragment(R.layout.fragment_books),
             booksAdapter = BooksAdapterGrid(requireContext(), this)
         }
         rv_bookshelf.adapter = booksAdapter
+        booksAdapter.registerAdapterDataObserver(object : RecyclerView.AdapterDataObserver() {
+            override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
+                val layoutManager = rv_bookshelf.layoutManager
+                if (positionStart == 0 && layoutManager is LinearLayoutManager) {
+                    val scrollTo = layoutManager.findFirstVisibleItemPosition() - itemCount
+                    rv_bookshelf.scrollToPosition(max(0, scrollTo))
+                }
+            }
+
+            override fun onItemRangeMoved(fromPosition: Int, toPosition: Int, itemCount: Int) {
+                val layoutManager = rv_bookshelf.layoutManager
+                if (toPosition == 0 && layoutManager is LinearLayoutManager) {
+                    val scrollTo = layoutManager.findFirstVisibleItemPosition() - itemCount
+                    rv_bookshelf.scrollToPosition(max(0, scrollTo))
+                }
+            }
+        })
     }
 
     private fun upRecyclerData() {