list: rework item arragement

Fix two issues with the ways items are laid out:
1. Remove the automatic span size lookup. Now that ConcatAdpater is
used, this basically becomes impossible to really leverage.
2. Use a divider item instead of a divider item decoration. The
latter is too buggy in many contexts, like the search view.

Resolves #426
Resolves #444

CHANGELOG.md

@@ -12,6 +12,8 @@ be parsed as images
 - Fixed issue where searches would match song file names case-sensitively
 - Fixed issue where the notification would not respond to changes in the album cover setting
 - Fixed issue where short names starting with an article would not be correctly sorted (ex. "the 1")
+- Fixed incorrect item arrangement on landscape
+- Fixed disappearing dividers in search view
 
 #### Dev/Meta
 - Switched to androidx media3 (New Home of ExoPlayer) for backing player components

app/src/main/java/org/oxycblt/auxio/IntegerTable.kt

@@ -37,16 +37,18 @@ object IntegerTable {
     const val VIEW_TYPE_PLAYLIST = 0xA004
     /** BasicHeaderViewHolder */
     const val VIEW_TYPE_BASIC_HEADER = 0xA005
+    /** DividerViewHolder */
+    const val VIEW_TYPE_DIVIDER = 0xA006
     /** SortHeaderViewHolder */
-    const val VIEW_TYPE_SORT_HEADER = 0xA006
+    const val VIEW_TYPE_SORT_HEADER = 0xA007
     /** AlbumSongViewHolder */
-    const val VIEW_TYPE_ALBUM_SONG = 0xA007
+    const val VIEW_TYPE_ALBUM_SONG = 0xA008
     /** ArtistAlbumViewHolder */
-    const val VIEW_TYPE_ARTIST_ALBUM = 0xA008
+    const val VIEW_TYPE_ARTIST_ALBUM = 0xA009
     /** ArtistSongViewHolder */
-    const val VIEW_TYPE_ARTIST_SONG = 0xA009
+    const val VIEW_TYPE_ARTIST_SONG = 0xA00A
     /** DiscHeaderViewHolder */
-    const val VIEW_TYPE_DISC_HEADER = 0xA00A
+    const val VIEW_TYPE_DISC_HEADER = 0xA00B
     /** "Music playback" notification code */
     const val PLAYBACK_NOTIFICATION_CODE = 0xA0A0
     /** "Music loading" notification code */

app/src/main/java/org/oxycblt/auxio/detail/AlbumDetailFragment.kt

@@ -26,6 +26,7 @@ import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
 import androidx.recyclerview.widget.ConcatAdapter
+import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.LinearSmoothScroller
 import com.google.android.material.transition.MaterialSharedAxis
 import dagger.hilt.android.AndroidEntryPoint
@@ -34,6 +35,8 @@ import org.oxycblt.auxio.databinding.FragmentDetailBinding
 import org.oxycblt.auxio.detail.header.AlbumDetailHeaderAdapter
 import org.oxycblt.auxio.detail.list.AlbumDetailListAdapter
 import org.oxycblt.auxio.detail.list.DetailListAdapter
+import org.oxycblt.auxio.list.Divider
+import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.ListFragment
 import org.oxycblt.auxio.list.Sort
@@ -45,6 +48,7 @@ import org.oxycblt.auxio.music.MusicMode
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.MusicViewModel
 import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.info.Disc
 import org.oxycblt.auxio.navigation.NavigationViewModel
 import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.util.*
@@ -95,7 +99,17 @@ class AlbumDetailFragment :
             setOnMenuItemClickListener(this@AlbumDetailFragment)
         }
 
-        binding.detailRecycler.adapter = ConcatAdapter(albumHeaderAdapter, albumListAdapter)
+        binding.detailRecycler.apply {
+            adapter = ConcatAdapter(albumHeaderAdapter, albumListAdapter)
+            (layoutManager as GridLayoutManager).setFullWidthLookup {
+                if (it != 0) {
+                    val item = detailModel.albumList.value[it - 1]
+                    item is Divider || item is Header || item is Disc
+                } else {
+                    true
+                }
+            }
+        }
 
         // -- VIEWMODEL SETUP ---
         // DetailViewModel handles most initialization from the navigation argument.

app/src/main/java/org/oxycblt/auxio/detail/ArtistDetailFragment.kt

@@ -26,6 +26,7 @@ import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
 import androidx.recyclerview.widget.ConcatAdapter
+import androidx.recyclerview.widget.GridLayoutManager
 import com.google.android.material.transition.MaterialSharedAxis
 import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
@@ -34,6 +35,8 @@ import org.oxycblt.auxio.detail.header.ArtistDetailHeaderAdapter
 import org.oxycblt.auxio.detail.header.DetailHeaderAdapter
 import org.oxycblt.auxio.detail.list.ArtistDetailListAdapter
 import org.oxycblt.auxio.detail.list.DetailListAdapter
+import org.oxycblt.auxio.list.Divider
+import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.ListFragment
 import org.oxycblt.auxio.list.Sort
@@ -94,7 +97,17 @@ class ArtistDetailFragment :
             setOnMenuItemClickListener(this@ArtistDetailFragment)
         }
 
-        binding.detailRecycler.adapter = ConcatAdapter(artistHeaderAdapter, artistListAdapter)
+        binding.detailRecycler.apply {
+            adapter = ConcatAdapter(artistHeaderAdapter, artistListAdapter)
+            (layoutManager as GridLayoutManager).setFullWidthLookup {
+                if (it != 0) {
+                    val item = detailModel.artistList.value[it - 1]
+                    item is Divider || item is Header
+                } else {
+                    true
+                }
+            }
+        }
 
         // --- VIEWMODEL SETUP ---
         // DetailViewModel handles most initialization from the navigation argument.

app/src/main/java/org/oxycblt/auxio/detail/DetailViewModel.kt

@@ -32,6 +32,7 @@ import kotlinx.coroutines.yield
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.detail.list.SortHeader
 import org.oxycblt.auxio.list.BasicHeader
+import org.oxycblt.auxio.list.Divider
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.list.adapter.UpdateInstructions
@@ -297,7 +298,9 @@ constructor(
     private fun refreshAlbumList(album: Album, replace: Boolean = false) {
         logD("Refreshing album list")
         val list = mutableListOf<Item>()
-        list.add(SortHeader(R.string.lbl_songs))
+        val header = SortHeader(R.string.lbl_songs)
+        list.add(Divider(header))
+        list.add(header)
         val instructions =
             if (replace) {
                 // Intentional so that the header item isn't replaced with the songs
@@ -355,7 +358,9 @@ constructor(
         logD("Release groups for this artist: ${byReleaseGroup.keys}")
 
         for (entry in byReleaseGroup.entries.sortedBy { it.key }) {
-            list.add(BasicHeader(entry.key.headerTitleRes))
+            val header = BasicHeader(entry.key.headerTitleRes)
+            list.add(Divider(header))
+            list.add(header)
             list.addAll(entry.value)
         }
 
@@ -363,7 +368,9 @@ constructor(
         var instructions: UpdateInstructions = UpdateInstructions.Diff
         if (artist.songs.isNotEmpty()) {
             logD("Songs present in this artist, adding header")
-            list.add(SortHeader(R.string.lbl_songs))
+            val header = SortHeader(R.string.lbl_songs)
+            list.add(Divider(header))
+            list.add(header)
             if (replace) {
                 // Intentional so that the header item isn't replaced with the songs
                 instructions = UpdateInstructions.Replace(list.size)
@@ -379,9 +386,14 @@ constructor(
         logD("Refreshing genre list")
         val list = mutableListOf<Item>()
         // Genre is guaranteed to always have artists and songs.
-        list.add(BasicHeader(R.string.lbl_artists))
+        val artistHeader = BasicHeader(R.string.lbl_artists)
+        list.add(Divider(artistHeader))
+        list.add(artistHeader)
         list.addAll(genre.artists)
-        list.add(SortHeader(R.string.lbl_songs))
+
+        val songHeader = SortHeader(R.string.lbl_songs)
+        list.add(Divider(songHeader))
+        list.add(songHeader)
         val instructions =
             if (replace) {
                 // Intentional so that the header item isn't replaced with the songs
@@ -400,7 +412,9 @@ constructor(
         val list = mutableListOf<Item>()
 
         if (playlist.songs.isNotEmpty()) {
-            list.add(SortHeader(R.string.lbl_songs))
+            val header = SortHeader(R.string.lbl_songs)
+            list.add(Divider(header))
+            list.add(header)
             if (replace) {
                 instructions = UpdateInstructions.Replace(list.size)
             }

app/src/main/java/org/oxycblt/auxio/detail/GenreDetailFragment.kt

@@ -26,6 +26,7 @@ import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
 import androidx.recyclerview.widget.ConcatAdapter
+import androidx.recyclerview.widget.GridLayoutManager
 import com.google.android.material.transition.MaterialSharedAxis
 import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
@@ -34,6 +35,8 @@ import org.oxycblt.auxio.detail.header.DetailHeaderAdapter
 import org.oxycblt.auxio.detail.header.GenreDetailHeaderAdapter
 import org.oxycblt.auxio.detail.list.DetailListAdapter
 import org.oxycblt.auxio.detail.list.GenreDetailListAdapter
+import org.oxycblt.auxio.list.Divider
+import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.ListFragment
 import org.oxycblt.auxio.list.Sort
@@ -87,7 +90,17 @@ class GenreDetailFragment :
             setOnMenuItemClickListener(this@GenreDetailFragment)
         }
 
-        binding.detailRecycler.adapter = ConcatAdapter(genreHeaderAdapter, genreListAdapter)
+        binding.detailRecycler.apply {
+            adapter = ConcatAdapter(genreHeaderAdapter, genreListAdapter)
+            (layoutManager as GridLayoutManager).setFullWidthLookup {
+                if (it != 0) {
+                    val item = detailModel.genreList.value[it - 1]
+                    item is Divider || item is Header
+                } else {
+                    true
+                }
+            }
+        }
 
         // --- VIEWMODEL SETUP ---
         // DetailViewModel handles most initialization from the navigation argument.

app/src/main/java/org/oxycblt/auxio/detail/PlaylistDetailFragment.kt

@@ -26,6 +26,7 @@ import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
 import androidx.recyclerview.widget.ConcatAdapter
+import androidx.recyclerview.widget.GridLayoutManager
 import com.google.android.material.transition.MaterialSharedAxis
 import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
@@ -34,6 +35,8 @@ import org.oxycblt.auxio.detail.header.DetailHeaderAdapter
 import org.oxycblt.auxio.detail.header.PlaylistDetailHeaderAdapter
 import org.oxycblt.auxio.detail.list.DetailListAdapter
 import org.oxycblt.auxio.detail.list.PlaylistDetailListAdapter
+import org.oxycblt.auxio.list.Divider
+import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.ListFragment
 import org.oxycblt.auxio.list.Sort
@@ -87,7 +90,17 @@ class PlaylistDetailFragment :
             setOnMenuItemClickListener(this@PlaylistDetailFragment)
         }
 
-        binding.detailRecycler.adapter = ConcatAdapter(playlistHeaderAdapter, playlistListAdapter)
+        binding.detailRecycler.apply {
+            adapter = ConcatAdapter(playlistHeaderAdapter, playlistListAdapter)
+            (layoutManager as GridLayoutManager).setFullWidthLookup {
+                if (it != 0) {
+                    val item = detailModel.playlistList.value[it - 1]
+                    item is Divider || item is Header
+                } else {
+                    true
+                }
+            }
+        }
 
         // --- VIEWMODEL SETUP ---
         // DetailViewModel handles most initialization from the navigation argument.

app/src/main/java/org/oxycblt/auxio/detail/list/AlbumDetailListAdapter.kt

@@ -69,15 +69,6 @@ class AlbumDetailListAdapter(private val listener: Listener<Song>) :
         }
     }
 
-    override fun isItemFullWidth(position: Int): Boolean {
-        if (super.isItemFullWidth(position)) {
-            return true
-        }
-        // The album and disc headers should be full-width in all configurations.
-        val item = getItem(position)
-        return item is Album || item is Disc
-    }
-
     private companion object {
         /** A comparator that can be used with DiffUtil. */
         val DIFF_CALLBACK =

app/src/main/java/org/oxycblt/auxio/detail/list/ArtistDetailListAdapter.kt

@@ -65,14 +65,6 @@ class ArtistDetailListAdapter(private val listener: Listener<Music>) :
         }
     }
 
-    override fun isItemFullWidth(position: Int): Boolean {
-        if (super.isItemFullWidth(position)) {
-            return true
-        }
-        // Artist headers should be full-width in all configurations.
-        return getItem(position) is Artist
-    }
-
     private companion object {
         /** A comparator that can be used with DiffUtil. */
         val DIFF_CALLBACK =

app/src/main/java/org/oxycblt/auxio/detail/list/DetailListAdapter.kt

@@ -27,6 +27,7 @@ import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.databinding.ItemSortHeaderBinding
 import org.oxycblt.auxio.list.BasicHeader
+import org.oxycblt.auxio.list.Divider
 import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.SelectableListListener
@@ -47,13 +48,12 @@ import org.oxycblt.auxio.util.inflater
 abstract class DetailListAdapter(
     private val listener: Listener<*>,
     private val diffCallback: DiffUtil.ItemCallback<Item>
-) :
+) : SelectionIndicatorAdapter<Item, RecyclerView.ViewHolder>(diffCallback) {
-    SelectionIndicatorAdapter<Item, RecyclerView.ViewHolder>(diffCallback),
-    AuxioRecyclerView.SpanSizeLookup {
 
     override fun getItemViewType(position: Int) =
         when (getItem(position)) {
             // Implement support for headers and sort headers
+            is Divider -> DividerViewHolder.VIEW_TYPE
             is BasicHeader -> BasicHeaderViewHolder.VIEW_TYPE
             is SortHeader -> SortHeaderViewHolder.VIEW_TYPE
             else -> super.getItemViewType(position)
@@ -61,6 +61,7 @@ abstract class DetailListAdapter(
 
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
         when (viewType) {
+            DividerViewHolder.VIEW_TYPE -> DividerViewHolder.from(parent)
             BasicHeaderViewHolder.VIEW_TYPE -> BasicHeaderViewHolder.from(parent)
             SortHeaderViewHolder.VIEW_TYPE -> SortHeaderViewHolder.from(parent)
             else -> error("Invalid item type $viewType")
@@ -73,12 +74,6 @@ abstract class DetailListAdapter(
         }
     }
 
-    override fun isItemFullWidth(position: Int): Boolean {
-        // Headers should be full-width in all configurations.
-        val item = getItem(position)
-        return item is BasicHeader || item is SortHeader
-    }
-
     /** An extended [SelectableListListener] for [DetailListAdapter] implementations. */
     interface Listener<in T : Music> : SelectableListListener<T> {
         /**
@@ -94,6 +89,8 @@ abstract class DetailListAdapter(
             object : SimpleDiffCallback<Item>() {
                 override fun areContentsTheSame(oldItem: Item, newItem: Item): Boolean {
                     return when {
+                        oldItem is Divider && newItem is Divider ->
+                            DividerViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is BasicHeader && newItem is BasicHeader ->
                             BasicHeaderViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is SortHeader && newItem is SortHeader ->

app/src/main/java/org/oxycblt/auxio/detail/list/GenreDetailListAdapter.kt

@@ -60,14 +60,6 @@ class GenreDetailListAdapter(private val listener: Listener<Music>) :
         }
     }
 
-    override fun isItemFullWidth(position: Int): Boolean {
-        if (super.isItemFullWidth(position)) {
-            return true
-        }
-        // Genre headers should be full-width in all configurations
-        return getItem(position) is Genre
-    }
-
     private companion object {
         val DIFF_CALLBACK =
             object : SimpleDiffCallback<Item>() {

app/src/main/java/org/oxycblt/auxio/detail/list/PlaylistDetailListAdapter.kt

@@ -56,14 +56,6 @@ class PlaylistDetailListAdapter(private val listener: Listener<Song>) :
         }
     }
 
-    override fun isItemFullWidth(position: Int): Boolean {
-        if (super.isItemFullWidth(position)) {
-            return true
-        }
-        // Playlist headers should be full-width in all configurations
-        return getItem(position) is Playlist
-    }
-
     companion object {
         val DIFF_CALLBACK =
             object : SimpleDiffCallback<Item>() {

app/src/main/java/org/oxycblt/auxio/list/Data.kt

@@ -40,3 +40,5 @@ interface Header : Item {
  * @author Alexander Capehart (OxygenCobalt)
  */
 data class BasicHeader(@StringRes override val titleRes: Int) : Header
+
+data class Divider(val anchor: Header?) : Item

app/src/main/java/org/oxycblt/auxio/list/recycler/AuxioRecyclerView.kt

@@ -23,14 +23,12 @@ import android.util.AttributeSet
 import android.view.WindowInsets
 import androidx.annotation.AttrRes
 import androidx.core.view.updatePadding
-import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.util.systemBarInsetsCompat
 
 /**
  * A [RecyclerView] with a few QoL extensions, such as:
  * - Automatic edge-to-edge support
- * - Adapter-based [SpanSizeLookup] implementation
  * - Automatic [setHasFixedSize] setup
  *
  * FIXME: Broken span configuration
@@ -49,7 +47,6 @@ constructor(context: Context, attrs: AttributeSet? = null, @AttrRes defStyleAttr
         // Auxio's non-dialog RecyclerViews never change their size based on adapter contents,
         // so we can enable fixed-size optimizations.
         setHasFixedSize(true)
-        addItemDecoration(HeaderItemDecoration(context))
     }
 
     final override fun setHasFixedSize(hasFixedSize: Boolean) {
@@ -67,36 +64,4 @@ constructor(context: Context, attrs: AttributeSet? = null, @AttrRes defStyleAttr
         updatePadding(bottom = initialPaddingBottom + insets.systemBarInsetsCompat.bottom)
         return insets
     }
-
-    override fun setAdapter(adapter: Adapter<*>?) {
-        super.setAdapter(adapter)
-
-        if (adapter is SpanSizeLookup) {
-            // This adapter has support for special span sizes, hook it up to the
-            // GridLayoutManager.
-            val glm = (layoutManager as GridLayoutManager)
-            val fullWidthSpanCount = glm.spanCount
-            glm.spanSizeLookup =
-                object : GridLayoutManager.SpanSizeLookup() {
-                    // Using the adapter implementation, if the adapter specifies that
-                    // an item is full width, it will take up all of the spans, using a
-                    // single span otherwise.
-                    override fun getSpanSize(position: Int) =
-                        if (adapter.isItemFullWidth(position)) fullWidthSpanCount else 1
-                }
-        }
-    }
-
-    /** A [RecyclerView.Adapter]-specific hook to control divider decoration visibility. */
-
-    /** An [RecyclerView.Adapter]-specific hook to [GridLayoutManager.SpanSizeLookup]. */
-    interface SpanSizeLookup {
-        /**
-         * Get if the item at a position takes up the whole width of the [RecyclerView] or not.
-         *
-         * @param position The position of the item.
-         * @return true if the item is full-width, false otherwise.
-         */
-        fun isItemFullWidth(position: Int): Boolean
-    }
 }

app/src/main/java/org/oxycblt/auxio/list/recycler/HeaderItemDecoration.kt

@@ -1,70 +0,0 @@
-/*
- * Copyright (c) 2023 Auxio Project
- * HeaderItemDecoration.kt is part of Auxio.
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
- 
-package org.oxycblt.auxio.list.recycler
-
-import android.content.Context
-import android.util.AttributeSet
-import androidx.recyclerview.widget.ConcatAdapter
-import androidx.recyclerview.widget.LinearLayoutManager
-import androidx.recyclerview.widget.RecyclerView
-import com.google.android.material.divider.BackportMaterialDividerItemDecoration
-import org.oxycblt.auxio.R
-import org.oxycblt.auxio.list.Header
-import org.oxycblt.auxio.list.adapter.FlexibleListAdapter
-
-/**
- * A [BackportMaterialDividerItemDecoration] that sets up the divider configuration to correctly
- * separate content with headers.
- *
- * @author Alexander Capehart (OxygenCobalt)
- */
-class HeaderItemDecoration
-@JvmOverloads
-constructor(
-    context: Context,
-    attributeSet: AttributeSet? = null,
-    defStyleAttr: Int = R.attr.materialDividerStyle,
-    orientation: Int = LinearLayoutManager.VERTICAL
-) : BackportMaterialDividerItemDecoration(context, attributeSet, defStyleAttr, orientation) {
-    override fun shouldDrawDivider(position: Int, adapter: RecyclerView.Adapter<*>?): Boolean {
-        if (adapter is ConcatAdapter) {
-            val adapterAndPosition =
-                try {
-                    adapter.getWrappedAdapterAndPosition(position + 1)
-                } catch (e: IllegalArgumentException) {
-                    return false
-                }
-            return hasHeaderAtPosition(adapterAndPosition.second, adapterAndPosition.first)
-        } else {
-            return hasHeaderAtPosition(position + 1, adapter)
-        }
-    }
-
-    private fun hasHeaderAtPosition(position: Int, adapter: RecyclerView.Adapter<*>?) =
-        try {
-            // Add a divider if the next item is a header. This organizes the divider to separate
-            // the ends of content rather than the beginning of content, alongside an added benefit
-            // of preventing top headers from having a divider applied.
-            (adapter as FlexibleListAdapter<*, *>).getItem(position) is Header
-        } catch (e: ClassCastException) {
-            false
-        } catch (e: IndexOutOfBoundsException) {
-            false
-        }
-}

app/src/main/java/org/oxycblt/auxio/list/recycler/ViewHolders.kt

@@ -22,10 +22,12 @@ import android.view.View
 import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.R
+import org.oxycblt.auxio.databinding.ItemDividerBinding
 import org.oxycblt.auxio.databinding.ItemHeaderBinding
 import org.oxycblt.auxio.databinding.ItemParentBinding
 import org.oxycblt.auxio.databinding.ItemSongBinding
 import org.oxycblt.auxio.list.BasicHeader
+import org.oxycblt.auxio.list.Divider
 import org.oxycblt.auxio.list.SelectableListListener
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.adapter.SimpleDiffCallback
@@ -246,7 +248,7 @@ class GenreViewHolder private constructor(private val binding: ItemParentBinding
         /** A comparator that can be used with DiffUtil. */
         val DIFF_CALLBACK =
             object : SimpleDiffCallback<Genre>() {
-                override fun areContentsTheSame(oldItem: Genre, newItem: Genre): Boolean =
+                override fun areContentsTheSame(oldItem: Genre, newItem: Genre) =
                     oldItem.name == newItem.name &&
                         oldItem.artists.size == newItem.artists.size &&
                         oldItem.songs.size == newItem.songs.size
@@ -304,7 +306,7 @@ class PlaylistViewHolder private constructor(private val binding: ItemParentBind
         /** A comparator that can be used with DiffUtil. */
         val DIFF_CALLBACK =
             object : SimpleDiffCallback<Playlist>() {
-                override fun areContentsTheSame(oldItem: Playlist, newItem: Playlist): Boolean =
+                override fun areContentsTheSame(oldItem: Playlist, newItem: Playlist) =
                     oldItem.name == newItem.name && oldItem.songs.size == newItem.songs.size
             }
     }
@@ -343,10 +345,38 @@ class BasicHeaderViewHolder private constructor(private val binding: ItemHeaderB
         /** A comparator that can be used with DiffUtil. */
         val DIFF_CALLBACK =
             object : SimpleDiffCallback<BasicHeader>() {
-                override fun areContentsTheSame(
+                override fun areContentsTheSame(oldItem: BasicHeader, newItem: BasicHeader) =
-                    oldItem: BasicHeader,
+                    oldItem.titleRes == newItem.titleRes
-                    newItem: BasicHeader
+            }
-                ): Boolean = oldItem.titleRes == newItem.titleRes
+    }
+}
+
+/**
+ * A [RecyclerView.ViewHolder] that displays a [Divider]. Use [from] to create an instance.
+ *
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class DividerViewHolder private constructor(private val binding: ItemDividerBinding) :
+    RecyclerView.ViewHolder(binding.root) {
+
+    companion object {
+        /** Unique ID for this ViewHolder type. */
+        const val VIEW_TYPE = IntegerTable.VIEW_TYPE_DIVIDER
+
+        /**
+         * Create a new instance.
+         *
+         * @param parent The parent to inflate this instance from.
+         * @return A new instance.
+         */
+        fun from(parent: View) =
+            DividerViewHolder(ItemDividerBinding.inflate(parent.context.inflater))
+
+        /** A comparator that can be used with DiffUtil. */
+        val DIFF_CALLBACK =
+            object : SimpleDiffCallback<Divider>() {
+                override fun areContentsTheSame(oldItem: Divider, newItem: Divider) =
+                    oldItem.anchor == newItem.anchor
             }
     }
 }

app/src/main/java/org/oxycblt/auxio/search/SearchAdapter.kt

@@ -34,8 +34,7 @@ import org.oxycblt.auxio.util.logD
  * @author Alexander Capehart (OxygenCobalt)
  */
 class SearchAdapter(private val listener: SelectableListListener<Music>) :
-    SelectionIndicatorAdapter<Item, RecyclerView.ViewHolder>(DIFF_CALLBACK),
+    SelectionIndicatorAdapter<Item, RecyclerView.ViewHolder>(DIFF_CALLBACK) {
-    AuxioRecyclerView.SpanSizeLookup {
 
     override fun getItemViewType(position: Int) =
         when (getItem(position)) {
@@ -44,6 +43,7 @@ class SearchAdapter(private val listener: SelectableListListener<Music>) :
             is Artist -> ArtistViewHolder.VIEW_TYPE
             is Genre -> GenreViewHolder.VIEW_TYPE
             is Playlist -> PlaylistViewHolder.VIEW_TYPE
+            is Divider -> DividerViewHolder.VIEW_TYPE
             is BasicHeader -> BasicHeaderViewHolder.VIEW_TYPE
             else -> super.getItemViewType(position)
         }
@@ -55,6 +55,7 @@ class SearchAdapter(private val listener: SelectableListListener<Music>) :
             ArtistViewHolder.VIEW_TYPE -> ArtistViewHolder.from(parent)
             GenreViewHolder.VIEW_TYPE -> GenreViewHolder.from(parent)
             PlaylistViewHolder.VIEW_TYPE -> PlaylistViewHolder.from(parent)
+            DividerViewHolder.VIEW_TYPE -> DividerViewHolder.from(parent)
             BasicHeaderViewHolder.VIEW_TYPE -> BasicHeaderViewHolder.from(parent)
             else -> error("Invalid item type $viewType")
         }
@@ -71,8 +72,6 @@ class SearchAdapter(private val listener: SelectableListListener<Music>) :
         }
     }
 
-    override fun isItemFullWidth(position: Int) = getItem(position) is BasicHeader
-
     private companion object {
         /** A comparator that can be used with DiffUtil. */
         val DIFF_CALLBACK =
@@ -87,6 +86,10 @@ class SearchAdapter(private val listener: SelectableListListener<Music>) :
                             ArtistViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is Genre && newItem is Genre ->
                             GenreViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
+                        oldItem is Playlist && newItem is Playlist ->
+                            PlaylistViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
+                        oldItem is Divider && newItem is Divider ->
+                            DividerViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is BasicHeader && newItem is BasicHeader ->
                             BasicHeaderViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         else -> false

app/src/main/java/org/oxycblt/auxio/search/SearchFragment.kt

@@ -29,10 +29,13 @@ import androidx.core.widget.addTextChangedListener
 import androidx.fragment.app.activityViewModels
 import androidx.fragment.app.viewModels
 import androidx.navigation.fragment.findNavController
+import androidx.recyclerview.widget.GridLayoutManager
 import com.google.android.material.transition.MaterialSharedAxis
 import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentSearchBinding
+import org.oxycblt.auxio.list.Divider
+import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.ListFragment
 import org.oxycblt.auxio.list.selection.SelectionViewModel
@@ -104,7 +107,13 @@ class SearchFragment : ListFragment<Music, FragmentSearchBinding>() {
             }
         }
 
-        binding.searchRecycler.adapter = searchAdapter
+        binding.searchRecycler.apply {
+            adapter = searchAdapter
+            (layoutManager as GridLayoutManager).setFullWidthLookup {
+                val item = searchModel.searchResults.value[it]
+                item is Divider || item is Header
+            }
+        }
 
         // --- VIEWMODEL SETUP ---
 

app/src/main/java/org/oxycblt/auxio/search/SearchViewModel.kt

@@ -30,6 +30,7 @@ import kotlinx.coroutines.launch
 import kotlinx.coroutines.yield
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.list.BasicHeader
+import org.oxycblt.auxio.list.Divider
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.music.*
@@ -138,23 +139,44 @@ constructor(
 
         return buildList {
             results.artists?.let {
-                add(BasicHeader(R.string.lbl_artists))
+                val header = BasicHeader(R.string.lbl_artists)
+                add(header)
                 addAll(SORT.artists(it))
             }
             results.albums?.let {
-                add(BasicHeader(R.string.lbl_albums))
+                val header = BasicHeader(R.string.lbl_albums)
+                if (isNotEmpty()) {
+                    add(Divider(header))
+                }
+
+                add(header)
                 addAll(SORT.albums(it))
             }
             results.playlists?.let {
-                add(BasicHeader(R.string.lbl_playlists))
+                val header = BasicHeader(R.string.lbl_playlists)
+                if (isNotEmpty()) {
+                    add(Divider(header))
+                }
+
+                add(header)
                 addAll(SORT.playlists(it))
             }
             results.genres?.let {
-                add(BasicHeader(R.string.lbl_genres))
+                val header = BasicHeader(R.string.lbl_genres)
+                if (isNotEmpty()) {
+                    add(Divider(header))
+                }
+
+                add(header)
                 addAll(SORT.genres(it))
             }
             results.songs?.let {
-                add(BasicHeader(R.string.lbl_songs))
+                val header = BasicHeader(R.string.lbl_songs)
+                if (isNotEmpty()) {
+                    add(Divider(header))
+                }
+
+                add(header)
                 addAll(SORT.songs(it))
             }
         }

app/src/main/java/org/oxycblt/auxio/util/FrameworkUtil.kt

@@ -31,6 +31,7 @@ import androidx.core.graphics.Insets
 import androidx.core.graphics.drawable.DrawableCompat
 import androidx.navigation.NavController
 import androidx.navigation.NavDirections
+import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import androidx.viewbinding.ViewBinding
 import java.lang.IllegalArgumentException
@@ -105,6 +106,20 @@ val ViewBinding.context: Context
  */
 fun RecyclerView.canScroll() = computeVerticalScrollRange() > height
 
+/**
+ * Shortcut to easily set up a [GridLayoutManager.SpanSizeLookup].
+ *
+ * @param isItemFullWidth Mapping expression that returns true if the item should take up all spans
+ *   or just one.
+ */
+fun GridLayoutManager.setFullWidthLookup(isItemFullWidth: (Int) -> Boolean) {
+    spanSizeLookup =
+        object : GridLayoutManager.SpanSizeLookup() {
+            override fun getSpanSize(position: Int) =
+                if (isItemFullWidth(position)) spanCount else 1
+        }
+}
+
 /**
  * Fix the double ripple that appears in MaterialButton instances due to an issue with AppCompat 1.5
  * or higher.

app/src/main/res/layout/item_divider.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<com.google.android.material.divider.MaterialDivider xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content" />