ViewPager2 perf: revert to ViewPager for episodes.

This will probably re-introduce bugs when the number of episodes changes (?), but this is worth the trade-off of much better paging performance.
UweTrottmann · Jan 12, 2024 · 6af22f6 · 6af22f6
1 parent 5b8f1ca
commit 6af22f6
Show file tree

Hide file tree

Showing 6 changed files with 57 additions and 38 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -16,6 +16,7 @@ Version 71
 *in development*
 
 * 🔧 Shows: adjust edit time dialog to avoid buttons moving around when changing values.
+* 🔧 Shows: faster scrolling between episode pages, again.
 * 🔧 Add acknowledgement messages for actions that may take longer (that do network requests), drop
   them for actions that complete immediately (e.g. set watched).
 * 🔨 Update Metacritic search links.

diff --git a/app/src/main/java/com/battlelancer/seriesguide/shows/episodes/EpisodePagerAdapter.kt b/app/src/main/java/com/battlelancer/seriesguide/shows/episodes/EpisodePagerAdapter.kt
@@ -4,49 +4,67 @@
 package com.battlelancer.seriesguide.shows.episodes
 
 import android.annotation.SuppressLint
+import android.content.Context
 import androidx.fragment.app.Fragment
-import androidx.fragment.app.FragmentActivity
-import androidx.recyclerview.widget.RecyclerView
-import androidx.viewpager2.adapter.FragmentStateAdapter
+import androidx.fragment.app.FragmentManager
+import androidx.fragment.app.FragmentStatePagerAdapter
 import com.battlelancer.seriesguide.shows.database.SgEpisode2Numbers
+import com.battlelancer.seriesguide.util.TextTools
 
 /**
  * Maps [Episode] objects to [EpisodeDetailsFragment] pages.
  */
-class EpisodePagerAdapter(
-    fragmentActivity: FragmentActivity
-) : FragmentStateAdapter(fragmentActivity) {
+@Suppress("DEPRECATION") // ViewPager2 paging performance is bad, don't need its improvements
+@SuppressLint("WrongConstant") // Behavior flag not recognized as valid.
+internal class EpisodePagerAdapter(
+    private val context: Context,
+    fm: FragmentManager
+) : FragmentStatePagerAdapter(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
 
-    private val items = ArrayList<SgEpisode2Numbers>()
+    private val episodes = ArrayList<SgEpisode2Numbers>()
 
-    @SuppressLint("NotifyDataSetChanged") // No need for incremental updates/animations.
-    fun updateItems(list: List<SgEpisode2Numbers>) {
-        items.clear()
-        items.addAll(list)
-        notifyDataSetChanged()
+    override fun getCount(): Int {
+        return episodes.size
+    }
+
+    override fun getItem(position: Int): Fragment {
+        return EpisodeDetailsFragment.newInstance(episodes[position].id)
+    }
+
+    override fun getItemPosition(`object`: Any): Int {
+        /*
+         * This breaks the FragmentStatePagerAdapter
+         * (see https://issuetracker.google.com/issues/36956111),
+         * so just destroy everything!
+         * Note: This might be fixed with ViewPager2.
+         */
+        // EpisodeDetailsFragment fragment = (EpisodeDetailsFragment)
+        // object;
+        // int episodeId = fragment.getEpisodeId();
+        // for (int i = 0; i < mEpisodes.size(); i++) {
+        // if (episodeId == mEpisodes.get(i).episodeId) {
+        // return i;
+        // }
+        // }
+        return POSITION_NONE
     }
 
     fun getItemEpisodeId(position: Int): Long? {
-        return if (position < items.size) {
-            items[position].id
+        return if (position < episodes.size) {
+            episodes[position].id
         } else {
             null
         }
     }
 
-    override fun getItemId(position: Int): Long {
-        return if (position < items.size) {
-            items[position].id
-        } else {
-            RecyclerView.NO_ID
-        }
+    override fun getPageTitle(position: Int): CharSequence? {
+        val episode = episodes[position]
+        return TextTools.getEpisodeNumber(context, episode.season, episode.episodenumber)
     }
 
-    override fun containsItem(itemId: Long): Boolean = items.find { it.id == itemId } != null
-
-    override fun getItemCount(): Int = items.size
-
-    override fun createFragment(position: Int): Fragment =
-        EpisodeDetailsFragment.newInstance(items[position].id)
-
+    fun updateEpisodeList(list: List<SgEpisode2Numbers>) {
+        episodes.clear()
+        episodes.addAll(list)
+        notifyDataSetChanged()
+    }
 }
diff --git a/app/src/main/java/com/battlelancer/seriesguide/shows/episodes/EpisodesActivity.kt b/app/src/main/java/com/battlelancer/seriesguide/shows/episodes/EpisodesActivity.kt
@@ -28,7 +28,6 @@ import com.battlelancer.seriesguide.shows.tools.ShowSync
 import com.battlelancer.seriesguide.ui.BaseMessageActivity
 import com.battlelancer.seriesguide.ui.OverviewActivity
 import com.battlelancer.seriesguide.util.ImageTools
-import com.battlelancer.seriesguide.util.TextTools
 import com.battlelancer.seriesguide.util.ThemeUtils
 import com.battlelancer.seriesguide.util.ThemeUtils.setDefaultStyle
 import com.google.android.material.shape.MaterialShapeDrawable
@@ -244,17 +243,18 @@ class EpisodesActivity : BaseMessageActivity() {
         val tabsEpisodes = binding.tabsEpisodes
         val adapter = episodeDetailsAdapter
         if (adapter == null) {
-            episodeDetailsAdapter = EpisodePagerAdapter(this)
-                .also { it.updateItems(info.episodes) }
+            episodeDetailsAdapter = EpisodePagerAdapter(
+                this,
+                supportFragmentManager
+            ).also {
+                it.updateEpisodeList(info.episodes)
+            }
             pagerEpisodes.adapter = episodeDetailsAdapter
         } else {
-            adapter.updateItems(info.episodes)
+            adapter.updateEpisodeList(info.episodes)
         }
         // Refresh pager tab decoration.
-        tabsEpisodes.setViewPager2(pagerEpisodes) { position ->
-            val episode = info.episodes[position]
-            TextTools.getEpisodeNumber(this, episode.season, episode.episodenumber)
-        }
+        tabsEpisodes.setViewPager(pagerEpisodes)
 
         // Remove page change listener to avoid changing checked episode on sort order changes.
         tabsEpisodes.setOnPageChangeListener(null)

diff --git a/app/src/main/res/layout-w1024dp/activity_episodes.xml b/app/src/main/res/layout-w1024dp/activity_episodes.xml
@@ -54,7 +54,7 @@
                     android:layout_width="match_parent"
                     android:layout_height="wrap_content" />
 
-                <androidx.viewpager2.widget.ViewPager2
+                <androidx.viewpager.widget.ViewPager
                     android:id="@+id/pagerEpisodes"
                     android:layout_width="match_parent"
                     android:layout_height="0dp"

diff --git a/app/src/main/res/layout-w590dp/activity_episodes.xml b/app/src/main/res/layout-w590dp/activity_episodes.xml
@@ -52,7 +52,7 @@
                     android:layout_height="wrap_content"
                     tools:layout_height="48dp" />
 
-                <androidx.viewpager2.widget.ViewPager2
+                <androidx.viewpager.widget.ViewPager
                     android:id="@+id/pagerEpisodes"
                     android:layout_width="match_parent"
                     android:layout_height="0dp"

diff --git a/app/src/main/res/layout/activity_episodes.xml b/app/src/main/res/layout/activity_episodes.xml
@@ -52,7 +52,7 @@
         android:orientation="vertical"
         app:layout_behavior="@string/appbar_scrolling_view_behavior">
 
-        <androidx.viewpager2.widget.ViewPager2
+        <androidx.viewpager.widget.ViewPager
             android:id="@+id/pagerEpisodes"
             android:layout_width="match_parent"
             android:layout_height="match_parent" />