From 577cc848eea6d34999cfc69b31c9527fc495f698 Mon Sep 17 00:00:00 2001
From: Koitharu <nvasya95@gmail.com>
Date: Sat, 28 Oct 2023 15:26:22 +0300
Subject: [PATCH] Scroll lists to top atomatically

---
 .../core/ui/list/RecyclerScrollKeeper.kt      | 40 +++++++++++++++++++
 .../download/ui/list/DownloadsActivity.kt     |  2 +
 .../kotatsu/history/ui/HistoryListFragment.kt |  2 +
 3 files changed, 44 insertions(+)
 create mode 100644 app/src/main/kotlin/org/koitharu/kotatsu/core/ui/list/RecyclerScrollKeeper.kt

diff --git a/app/src/main/kotlin/org/koitharu/kotatsu/core/ui/list/RecyclerScrollKeeper.kt b/app/src/main/kotlin/org/koitharu/kotatsu/core/ui/list/RecyclerScrollKeeper.kt
new file mode 100644
index 000000000..b6d651e46
--- /dev/null
+++ b/app/src/main/kotlin/org/koitharu/kotatsu/core/ui/list/RecyclerScrollKeeper.kt
@@ -0,0 +1,40 @@
+package org.koitharu.kotatsu.core.ui.list
+
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.RecyclerView.AdapterDataObserver
+
+class RecyclerScrollKeeper(
+	private val rv: RecyclerView,
+) : AdapterDataObserver() {
+
+	private val scrollUpRunnable = Runnable {
+		(rv.layoutManager as? LinearLayoutManager)?.scrollToPositionWithOffset(0, 0)
+	}
+
+	fun attach() {
+		rv.adapter?.registerAdapterDataObserver(this)
+	}
+
+	override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
+		super.onItemRangeInserted(positionStart, itemCount)
+		if (positionStart == 0 && isScrolledToTop()) {
+			postScrollUp()
+		}
+	}
+
+	override fun onItemRangeMoved(fromPosition: Int, toPosition: Int, itemCount: Int) {
+		super.onItemRangeMoved(fromPosition, toPosition, itemCount)
+		if (toPosition == 0 && isScrolledToTop()) {
+			postScrollUp()
+		}
+	}
+
+	private fun postScrollUp() {
+		rv.postDelayed(scrollUpRunnable, 500L)
+	}
+
+	private fun isScrolledToTop(): Boolean {
+		return (rv.layoutManager as? LinearLayoutManager)?.findFirstVisibleItemPosition() == 0
+	}
+}
diff --git a/app/src/main/kotlin/org/koitharu/kotatsu/download/ui/list/DownloadsActivity.kt b/app/src/main/kotlin/org/koitharu/kotatsu/download/ui/list/DownloadsActivity.kt
index f01eb4803..e7487bbc8 100644
--- a/app/src/main/kotlin/org/koitharu/kotatsu/download/ui/list/DownloadsActivity.kt
+++ b/app/src/main/kotlin/org/koitharu/kotatsu/download/ui/list/DownloadsActivity.kt
@@ -15,6 +15,7 @@ import dagger.hilt.android.AndroidEntryPoint
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.ui.BaseActivity
 import org.koitharu.kotatsu.core.ui.list.ListSelectionController
+import org.koitharu.kotatsu.core.ui.list.RecyclerScrollKeeper
 import org.koitharu.kotatsu.core.ui.util.MenuInvalidator
 import org.koitharu.kotatsu.core.ui.util.ReversibleActionObserver
 import org.koitharu.kotatsu.core.util.ext.observe
@@ -53,6 +54,7 @@ class DownloadsActivity : BaseActivity<ActivityDownloadsBinding>(),
 			addItemDecoration(decoration)
 			adapter = downloadsAdapter
 			selectionController.attachToRecyclerView(this)
+			RecyclerScrollKeeper(this).attach()
 		}
 		addMenuProvider(DownloadsMenuProvider(this, viewModel))
 		viewModel.items.observe(this) {
diff --git a/app/src/main/kotlin/org/koitharu/kotatsu/history/ui/HistoryListFragment.kt b/app/src/main/kotlin/org/koitharu/kotatsu/history/ui/HistoryListFragment.kt
index 56837477a..ed6a4718e 100644
--- a/app/src/main/kotlin/org/koitharu/kotatsu/history/ui/HistoryListFragment.kt
+++ b/app/src/main/kotlin/org/koitharu/kotatsu/history/ui/HistoryListFragment.kt
@@ -9,6 +9,7 @@ import dagger.hilt.android.AndroidEntryPoint
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.os.NetworkManageIntent
 import org.koitharu.kotatsu.core.ui.list.ListSelectionController
+import org.koitharu.kotatsu.core.ui.list.RecyclerScrollKeeper
 import org.koitharu.kotatsu.core.util.ext.addMenuProvider
 import org.koitharu.kotatsu.databinding.FragmentListBinding
 import org.koitharu.kotatsu.list.ui.MangaListFragment
@@ -23,6 +24,7 @@ class HistoryListFragment : MangaListFragment() {
 
 	override fun onViewBindingCreated(binding: FragmentListBinding, savedInstanceState: Bundle?) {
 		super.onViewBindingCreated(binding, savedInstanceState)
+		RecyclerScrollKeeper(binding.recyclerView).attach()
 		addMenuProvider(HistoryListMenuProvider(binding.root.context, viewModel))
 	}