From 8d7d45a26710233c71b4d7e2f777c228660c6712 Mon Sep 17 00:00:00 2001
From: Matthieu <24-artectrex@users.noreply.shinice.net>
Date: Sat, 22 May 2021 13:03:13 +0200
Subject: [PATCH] smooth scroll instead of jump

---
 .../feeds/cachedFeeds/CachedFeedFragment.kt   |  4 ++-
 .../java/org/pixeldroid/app/utils/Utils.kt    | 25 +++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/app/src/main/java/org/pixeldroid/app/posts/feeds/cachedFeeds/CachedFeedFragment.kt b/app/src/main/java/org/pixeldroid/app/posts/feeds/cachedFeeds/CachedFeedFragment.kt
index b8484efe..57ace3a4 100644
--- a/app/src/main/java/org/pixeldroid/app/posts/feeds/cachedFeeds/CachedFeedFragment.kt
+++ b/app/src/main/java/org/pixeldroid/app/posts/feeds/cachedFeeds/CachedFeedFragment.kt
@@ -9,6 +9,7 @@ import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.lifecycleScope
 import androidx.paging.*
 import androidx.paging.LoadState.*
+import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.*
@@ -18,6 +19,7 @@ import org.pixeldroid.app.utils.BaseFragment
 import org.pixeldroid.app.utils.api.objects.FeedContentDatabase
 import org.pixeldroid.app.utils.db.AppDatabase
 import org.pixeldroid.app.utils.db.dao.feedContent.FeedContentDao
+import org.pixeldroid.app.utils.limitedLengthSmoothScrollToPosition
 
 /**
  * A fragment representing a list of [FeedContentDatabase] items that are cached by the database.
@@ -78,7 +80,7 @@ open class CachedFeedFragment<T: FeedContentDatabase> : BaseFragment() {
     }
 
     fun onTabReClicked() {
-        binding.list.scrollToPosition(0)
+        binding.list.limitedLengthSmoothScrollToPosition(0)
     }
 }
 
diff --git a/app/src/main/java/org/pixeldroid/app/utils/Utils.kt b/app/src/main/java/org/pixeldroid/app/utils/Utils.kt
index 4de86c61..8769881b 100644
--- a/app/src/main/java/org/pixeldroid/app/utils/Utils.kt
+++ b/app/src/main/java/org/pixeldroid/app/utils/Utils.kt
@@ -15,6 +15,8 @@ import androidx.browser.customtabs.CustomTabsIntent
 import androidx.fragment.app.Fragment
 import androidx.lifecycle.DefaultLifecycleObserver
 import androidx.lifecycle.LifecycleOwner
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
 import org.pixeldroid.app.R
 import okhttp3.HttpUrl
 import kotlin.properties.ReadWriteProperty
@@ -79,6 +81,29 @@ fun BaseActivity.openUrl(url: String): Boolean{
     }
 }
 
+
+fun RecyclerView.limitedLengthSmoothScrollToPosition(targetItem: Int) {
+    layoutManager?.apply {
+        val maxScroll = 3
+        when (this) {
+            is LinearLayoutManager -> {
+                val topItem = findFirstVisibleItemPosition()
+                val distance = topItem - targetItem
+                val anchorItem = when {
+                    distance > maxScroll -> targetItem + maxScroll
+                    distance < -maxScroll -> targetItem - maxScroll
+                    else -> topItem
+                }
+                if (anchorItem != topItem) scrollToPosition(anchorItem)
+                post {
+                    smoothScrollToPosition(targetItem)
+                }
+            }
+            else -> smoothScrollToPosition(targetItem)
+        }
+    }
+}
+
 /**
  * @brief Updates the application's theme depending on the given preferences and resources
  */