home: indicate playback on items [#218]

Indicate playback in the home view as well.

This is mostly a QoL change. Might also add this to the search view.

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

@@ -257,10 +257,10 @@ class AlbumDetailFragment :
         }
 
         if (parent is Album && parent.id == unlikelyToBeNull(detailModel.currentAlbum.value).id) {
-            detailAdapter.highlightSong(song)
+            detailAdapter.activateSong(song)
         } else {
             // Clear the ViewHolders if the mode isn't ALL_SONGS
-            detailAdapter.highlightSong(null)
+            detailAdapter.activateSong(null)
         }
     }
 

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

@@ -202,18 +202,18 @@ class ArtistDetailFragment :
 
     private fun updatePlayback(song: Song?, parent: MusicParent?) {
         if (parent is Artist && parent.id == unlikelyToBeNull(detailModel.currentArtist.value).id) {
-            detailAdapter.highlightSong(song)
+            detailAdapter.activateSong(song)
         } else {
-            // Clear the ViewHolders if the given song is not part of this artist.
+            // Ignore song playback not from the artist
-            detailAdapter.highlightSong(null)
+            detailAdapter.activateSong(null)
         }
 
         if (parent is Album &&
             parent.artist.id == unlikelyToBeNull(detailModel.currentArtist.value).id) {
-            detailAdapter.highlightAlbum(parent)
+            detailAdapter.activateAlbum(parent)
         } else {
-            // Clear out the album viewholder if the parent is not an album.
+            // Ignore album playback not from the artist
-            detailAdapter.highlightAlbum(null)
+            detailAdapter.activateAlbum(null)
         }
     }
 }

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

@@ -83,7 +83,7 @@ class GenreDetailFragment :
         binding.detailRecycler.apply {
             adapter = detailAdapter
             setSpanSizeLookup { pos ->
-                val item = detailModel.albumData.value[pos]
+                val item = detailModel.genreData.value[pos]
                 item is Genre || item is Header || item is SortHeader
             }
         }
@@ -195,9 +195,10 @@ class GenreDetailFragment :
 
     private fun updatePlayback(song: Song?, parent: MusicParent?) {
         if (parent is Genre && parent.id == unlikelyToBeNull(detailModel.currentGenre.value).id) {
-            detailAdapter.highlightSong(song)
+            detailAdapter.activateSong(song)
         } else {
-            detailAdapter.highlightSong(null)
+            // Ignore song playback not from the genre
+            detailAdapter.activateSong(null)
         }
     }
 }

app/src/main/java/org/oxycblt/auxio/detail/recycler/AlbumDetailAdapter.kt

@@ -64,25 +64,28 @@ class AlbumDetailAdapter(private val listener: Listener) :
     override fun onBindViewHolder(
         holder: RecyclerView.ViewHolder,
         position: Int,
-        payload: List<Any>
+        payloads: List<Any>
     ) {
-        if (payload.isEmpty()) {
+        super.onBindViewHolder(holder, position, payloads)
+
+        if (payloads.isEmpty()) {
             when (val item = differ.currentList[position]) {
                 is Album -> (holder as AlbumDetailViewHolder).bind(item, listener)
                 is DiscHeader -> (holder as DiscHeaderViewHolder).bind(item)
                 is Song -> (holder as AlbumSongViewHolder).bind(item, listener)
             }
         }
-
-        super.onBindViewHolder(holder, position, payload)
     }
 
-    override fun shouldHighlightViewHolder(item: Item) = item is Song && item.id == currentSong?.id
+    override fun shouldActivateViewHolder(position: Int): Boolean {
+        val item = differ.currentList[position]
+        return item is Song && item.id == currentSong?.id
+    }
 
-    /** Update the [song] that this adapter should highlight */
+    /** Update the [song] that this adapter should indicate playback */
-    fun highlightSong(song: Song?) {
+    fun activateSong(song: Song?) {
         if (song == currentSong) return
-        highlightImpl(currentSong, song)
+        activateImpl(differ.currentList, currentSong, song)
         currentSong = song
     }
 

app/src/main/java/org/oxycblt/auxio/detail/recycler/ArtistDetailAdapter.kt

@@ -66,34 +66,36 @@ class ArtistDetailAdapter(private val listener: Listener) :
     override fun onBindViewHolder(
         holder: RecyclerView.ViewHolder,
         position: Int,
-        payload: List<Any>
+        payloads: List<Any>
     ) {
-        if (payload.isEmpty()) {
+        super.onBindViewHolder(holder, position, payloads)
+
+        if (payloads.isEmpty()) {
             when (val item = differ.currentList[position]) {
                 is Artist -> (holder as ArtistDetailViewHolder).bind(item, listener)
                 is Album -> (holder as ArtistAlbumViewHolder).bind(item, listener)
                 is Song -> (holder as ArtistSongViewHolder).bind(item, listener)
             }
         }
-
-        super.onBindViewHolder(holder, position, payload)
     }
 
-    override fun shouldHighlightViewHolder(item: Item) =
+    override fun shouldActivateViewHolder(position: Int): Boolean {
-        (item is Album && item.id == currentAlbum?.id) ||
+        val item = differ.currentList[position]
+        return (item is Album && item.id == currentAlbum?.id) ||
             (item is Song && item.id == currentSong?.id)
+    }
 
-    /** Update the current [album] that this adapter should highlight */
+    /** Update the [album] that this adapter should indicate playback */
-    fun highlightAlbum(album: Album?) {
+    fun activateAlbum(album: Album?) {
         if (album == currentAlbum) return
-        highlightImpl(currentAlbum, album)
+        activateImpl(differ.currentList, currentAlbum, album)
         currentAlbum = album
     }
 
-    /** Update the [song] that this adapter should highlight */
+    /** Update the [song] that this adapter should indicate playback */
-    fun highlightSong(song: Song?) {
+    fun activateSong(song: Song?) {
         if (song == currentSong) return
-        highlightImpl(currentSong, song)
+        activateImpl(differ.currentList, currentSong, song)
         currentSong = song
     }
 

app/src/main/java/org/oxycblt/auxio/detail/recycler/DetailAdapter.kt

@@ -26,6 +26,7 @@ import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.databinding.ItemSortHeaderBinding
 import org.oxycblt.auxio.detail.SortHeader
+import org.oxycblt.auxio.ui.recycler.ActivationAdapter
 import org.oxycblt.auxio.ui.recycler.Header
 import org.oxycblt.auxio.ui.recycler.HeaderViewHolder
 import org.oxycblt.auxio.ui.recycler.Item
@@ -33,12 +34,11 @@ import org.oxycblt.auxio.ui.recycler.MenuItemListener
 import org.oxycblt.auxio.ui.recycler.SimpleItemCallback
 import org.oxycblt.auxio.util.context
 import org.oxycblt.auxio.util.inflater
-import org.oxycblt.auxio.util.logW
 
 abstract class DetailAdapter<L : DetailAdapter.Listener>(
     private val listener: L,
     diffCallback: DiffUtil.ItemCallback<Item>
-) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
+) : ActivationAdapter<RecyclerView.ViewHolder>() {
     @Suppress("LeakingThis") override fun getItemCount() = differ.currentList.size
 
     override fun getItemViewType(position: Int) =
@@ -61,58 +61,27 @@ abstract class DetailAdapter<L : DetailAdapter.Listener>(
     override fun onBindViewHolder(
         holder: RecyclerView.ViewHolder,
         position: Int,
-        payload: List<Any>
+        payloads: List<Any>
     ) {
         val item = differ.currentList[position]
 
-        if (payload.isEmpty()) {
+        if (payloads.isEmpty()) {
             when (item) {
                 is Header -> (holder as HeaderViewHolder).bind(item)
                 is SortHeader -> (holder as SortHeaderViewHolder).bind(item, listener)
             }
         }
 
-        holder.itemView.isActivated = shouldHighlightViewHolder(item)
+        super.onBindViewHolder(holder, position, payloads)
     }
 
     protected val differ = AsyncListDiffer(this, diffCallback)
 
-    protected abstract fun shouldHighlightViewHolder(item: Item): Boolean
-
-    protected inline fun <reified T : Item> highlightImpl(oldItem: T?, newItem: T?) {
-        if (oldItem != null) {
-            val pos = differ.currentList.indexOfFirst { item -> item.id == oldItem.id && item is T }
-
-            if (pos > -1) {
-                notifyItemChanged(pos, PAYLOAD_HIGHLIGHT_CHANGED)
-            } else {
-                logW("oldItem was not in adapter data")
-            }
-        }
-
-        if (newItem != null) {
-            val pos = differ.currentList.indexOfFirst { item -> item is T && item.id == newItem.id }
-
-            if (pos > -1) {
-                notifyItemChanged(pos, PAYLOAD_HIGHLIGHT_CHANGED)
-            } else {
-                logW("newItem was not in adapter data")
-            }
-        }
-    }
-
     fun submitList(list: List<Item>) {
         differ.submitList(list)
     }
 
     companion object {
-        // This payload value serves two purposes:
-        // 1. It disables animations from notifyItemChanged, which looks bad when highlighting
-        // ViewHolders.
-        // 2. It instructs adapters to avoid re-binding information, and instead simply
-        // change the highlight state.
-        val PAYLOAD_HIGHLIGHT_CHANGED = Any()
-
         val DIFFER =
             object : SimpleItemCallback<Item>() {
                 override fun areItemsTheSame(oldItem: Item, newItem: Item): Boolean {

app/src/main/java/org/oxycblt/auxio/detail/recycler/GenreDetailAdapter.kt

@@ -58,24 +58,27 @@ class GenreDetailAdapter(private val listener: Listener) :
     override fun onBindViewHolder(
         holder: RecyclerView.ViewHolder,
         position: Int,
-        payload: List<Any>
+        payloads: List<Any>
     ) {
-        if (payload.isEmpty()) {
+        super.onBindViewHolder(holder, position, payloads)
+
+        if (payloads.isEmpty()) {
             when (val item = differ.currentList[position]) {
                 is Genre -> (holder as GenreDetailViewHolder).bind(item, listener)
                 is Song -> (holder as SongViewHolder).bind(item, listener)
             }
         }
-
-        super.onBindViewHolder(holder, position, payload)
     }
 
-    override fun shouldHighlightViewHolder(item: Item) = item is Song && item.id == currentSong?.id
+    override fun shouldActivateViewHolder(position: Int): Boolean {
+        val item = differ.currentList[position]
+        return item is Song && item.id == currentSong?.id
+    }
 
-    /** Update the [song] that this adapter should highlight */
+    /** Update the [song] that this adapter should indicate playback */
-    fun highlightSong(song: Song?) {
+    fun activateSong(song: Song?) {
         if (song == currentSong) return
-        highlightImpl(currentSong, song)
+        activateImpl(differ.currentList, currentSong, song)
         currentSong = song
     }
 

app/src/main/java/org/oxycblt/auxio/home/list/AlbumListFragment.kt

@@ -21,14 +21,15 @@ import android.os.Bundle
 import android.text.format.DateUtils
 import android.view.View
 import android.view.ViewGroup
-import androidx.recyclerview.widget.RecyclerView
 import java.util.*
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentHomeListBinding
 import org.oxycblt.auxio.music.Album
 import org.oxycblt.auxio.music.Music
+import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.ui.DisplayMode
 import org.oxycblt.auxio.ui.Sort
+import org.oxycblt.auxio.ui.recycler.ActivationAdapter
 import org.oxycblt.auxio.ui.recycler.AlbumViewHolder
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.ui.recycler.MenuItemListener
@@ -55,6 +56,7 @@ class AlbumListFragment : HomeListFragment<Album>() {
         }
 
         collectImmediately(homeModel.albums, homeAdapter::replaceList)
+        collectImmediately(playbackModel.parent, ::handleParent)
     }
 
     override fun getPopup(pos: Int): String? {
@@ -107,21 +109,47 @@ class AlbumListFragment : HomeListFragment<Album>() {
         }
     }
 
+    private fun handleParent(parent: MusicParent?) {
+        if (parent is Album) {
+            homeAdapter.activateAlbum(parent)
+        } else {
+            // Ignore playback not from albums
+            homeAdapter.activateAlbum(null)
+        }
+    }
+
     private class AlbumAdapter(private val listener: MenuItemListener) :
-        RecyclerView.Adapter<AlbumViewHolder>() {
+        ActivationAdapter<AlbumViewHolder>() {
         private val differ = SyncListDiffer(this, AlbumViewHolder.DIFFER)
+        private var currentAlbum: Album? = null
 
         override fun getItemCount() = differ.currentList.size
 
         override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
             AlbumViewHolder.new(parent)
 
-        override fun onBindViewHolder(holder: AlbumViewHolder, position: Int) {
+        override fun onBindViewHolder(holder: AlbumViewHolder, position: Int, payloads: List<Any>) {
-            holder.bind(differ.currentList[position], listener)
+            super.onBindViewHolder(holder, position, payloads)
+
+            if (payloads.isEmpty()) {
+                holder.bind(differ.currentList[position], listener)
+            }
+        }
+
+        override fun shouldActivateViewHolder(position: Int): Boolean {
+            val item = differ.currentList[position]
+            return item.id == currentAlbum?.id
         }
 
         fun replaceList(newList: List<Album>) {
             differ.replaceList(newList)
         }
+
+        /** Update the [album] that this adapter should indicate playback */
+        fun activateAlbum(album: Album?) {
+            if (album == currentAlbum) return
+            activateImpl(differ.currentList, currentAlbum, album)
+            currentAlbum = album
+        }
     }
 }

app/src/main/java/org/oxycblt/auxio/home/list/ArtistListFragment.kt

@@ -20,13 +20,14 @@ package org.oxycblt.auxio.home.list
 import android.os.Bundle
 import android.view.View
 import android.view.ViewGroup
-import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentHomeListBinding
 import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Music
+import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.ui.DisplayMode
 import org.oxycblt.auxio.ui.Sort
+import org.oxycblt.auxio.ui.recycler.ActivationAdapter
 import org.oxycblt.auxio.ui.recycler.ArtistViewHolder
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.ui.recycler.MenuItemListener
@@ -50,6 +51,7 @@ class ArtistListFragment : HomeListFragment<Artist>() {
         }
 
         collectImmediately(homeModel.artists, homeAdapter::replaceList)
+        collectImmediately(playbackModel.parent, ::handleParent)
     }
 
     override fun getPopup(pos: Int): String? {
@@ -83,21 +85,51 @@ class ArtistListFragment : HomeListFragment<Artist>() {
         }
     }
 
+    private fun handleParent(parent: MusicParent?) {
+        if (parent is Artist) {
+            homeAdapter.activateArtist(parent)
+        } else {
+            // Ignore playback not from artists
+            homeAdapter.activateArtist(null)
+        }
+    }
+
     private class ArtistAdapter(private val listener: MenuItemListener) :
-        RecyclerView.Adapter<ArtistViewHolder>() {
+        ActivationAdapter<ArtistViewHolder>() {
         private val differ = SyncListDiffer(this, ArtistViewHolder.DIFFER)
+        private var currentArtist: Artist? = null
 
         override fun getItemCount() = differ.currentList.size
 
         override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
             ArtistViewHolder.new(parent)
 
-        override fun onBindViewHolder(holder: ArtistViewHolder, position: Int) {
+        override fun onBindViewHolder(
-            holder.bind(differ.currentList[position], listener)
+            holder: ArtistViewHolder,
+            position: Int,
+            payloads: List<Any>
+        ) {
+            super.onBindViewHolder(holder, position, payloads)
+
+            if (payloads.isEmpty()) {
+                holder.bind(differ.currentList[position], listener)
+            }
+        }
+
+        override fun shouldActivateViewHolder(position: Int): Boolean {
+            val item = differ.currentList[position]
+            return item.id == currentArtist?.id
         }
 
         fun replaceList(newList: List<Artist>) {
             differ.replaceList(newList)
         }
+
+        /** Update the [artist] that this adapter should indicate playback */
+        fun activateArtist(artist: Artist?) {
+            if (artist == currentArtist) return
+            activateImpl(differ.currentList, currentArtist, artist)
+            currentArtist = artist
+        }
     }
 }

app/src/main/java/org/oxycblt/auxio/home/list/GenreListFragment.kt

@@ -20,13 +20,14 @@ package org.oxycblt.auxio.home.list
 import android.os.Bundle
 import android.view.View
 import android.view.ViewGroup
-import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentHomeListBinding
 import org.oxycblt.auxio.music.Genre
 import org.oxycblt.auxio.music.Music
+import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.ui.DisplayMode
 import org.oxycblt.auxio.ui.Sort
+import org.oxycblt.auxio.ui.recycler.ActivationAdapter
 import org.oxycblt.auxio.ui.recycler.GenreViewHolder
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.ui.recycler.MenuItemListener
@@ -50,6 +51,7 @@ class GenreListFragment : HomeListFragment<Genre>() {
         }
 
         collectImmediately(homeModel.genres, homeAdapter::replaceList)
+        collectImmediately(playbackModel.parent, ::handlePlayback)
     }
 
     override fun getPopup(pos: Int): String? {
@@ -83,21 +85,47 @@ class GenreListFragment : HomeListFragment<Genre>() {
         }
     }
 
+    private fun handlePlayback(parent: MusicParent?) {
+        if (parent is Genre) {
+            homeAdapter.activateGenre(parent)
+        } else {
+            // Ignore playback not from genres
+            homeAdapter.activateGenre(null)
+        }
+    }
+
     private class GenreAdapter(private val listener: MenuItemListener) :
-        RecyclerView.Adapter<GenreViewHolder>() {
+        ActivationAdapter<GenreViewHolder>() {
         private val differ = SyncListDiffer(this, GenreViewHolder.DIFFER)
+        private var currentGenre: Genre? = null
 
         override fun getItemCount() = differ.currentList.size
 
         override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
             GenreViewHolder.new(parent)
 
-        override fun onBindViewHolder(holder: GenreViewHolder, position: Int) {
+        override fun onBindViewHolder(holder: GenreViewHolder, position: Int, payloads: List<Any>) {
-            holder.bind(differ.currentList[position], listener)
+            super.onBindViewHolder(holder, position, payloads)
+
+            if (payloads.isEmpty()) {
+                holder.bind(differ.currentList[position], listener)
+            }
+        }
+
+        override fun shouldActivateViewHolder(position: Int): Boolean {
+            val item = differ.currentList[position]
+            return item.id == currentGenre?.id
         }
 
         fun replaceList(newList: List<Genre>) {
             differ.replaceList(newList)
         }
+
+        /** Update the [genre] that this adapter should indicate playback */
+        fun activateGenre(genre: Genre?) {
+            if (genre == currentGenre) return
+            activateImpl(differ.currentList, currentGenre, genre)
+            currentGenre = genre
+        }
     }
 }

app/src/main/java/org/oxycblt/auxio/home/list/SongListFragment.kt

@@ -21,14 +21,15 @@ import android.os.Bundle
 import android.text.format.DateUtils
 import android.view.View
 import android.view.ViewGroup
-import androidx.recyclerview.widget.RecyclerView
 import java.util.Formatter
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentHomeListBinding
+import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.settings.Settings
 import org.oxycblt.auxio.ui.DisplayMode
 import org.oxycblt.auxio.ui.Sort
+import org.oxycblt.auxio.ui.recycler.ActivationAdapter
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.ui.recycler.MenuItemListener
 import org.oxycblt.auxio.ui.recycler.SongViewHolder
@@ -57,6 +58,7 @@ class SongListFragment : HomeListFragment<Song>() {
         }
 
         collectImmediately(homeModel.songs, homeAdapter::replaceList)
+        collectImmediately(playbackModel.song, playbackModel.parent, ::handlePlayback)
     }
 
     override fun getPopup(pos: Int): String? {
@@ -111,21 +113,47 @@ class SongListFragment : HomeListFragment<Song>() {
         }
     }
 
+    private fun handlePlayback(song: Song?, parent: MusicParent?) {
+        if (parent == null) {
+            homeAdapter.activateSong(song)
+        } else {
+            // Ignore playback that is not from all songs
+            homeAdapter.activateSong(null)
+        }
+    }
+
     private class SongAdapter(private val listener: MenuItemListener) :
-        RecyclerView.Adapter<SongViewHolder>() {
+        ActivationAdapter<SongViewHolder>() {
         private val differ = SyncListDiffer(this, SongViewHolder.DIFFER)
+        private var currentSong: Song? = null
 
         override fun getItemCount() = differ.currentList.size
 
         override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
             SongViewHolder.new(parent)
 
-        override fun onBindViewHolder(holder: SongViewHolder, position: Int) {
+        override fun onBindViewHolder(holder: SongViewHolder, position: Int, payloads: List<Any>) {
-            holder.bind(differ.currentList[position], listener)
+            super.onBindViewHolder(holder, position, payloads)
+
+            if (payloads.isEmpty()) {
+                holder.bind(differ.currentList[position], listener)
+            }
+        }
+
+        override fun shouldActivateViewHolder(position: Int): Boolean {
+            val item = differ.currentList[position]
+            return item.id == currentSong?.id
         }
 
         fun replaceList(newList: List<Song>) {
             differ.replaceList(newList)
         }
+
+        /** Update the [song] that this adapter should indicate playback */
+        fun activateSong(song: Song?) {
+            if (song == currentSong) return
+            activateImpl(differ.currentList, currentSong, song)
+            currentSong = song
+        }
     }
 }

app/src/main/java/org/oxycblt/auxio/ui/recycler/RecyclerFramework.kt

@@ -23,6 +23,7 @@ import androidx.recyclerview.widget.AdapterListUpdateCallback
 import androidx.recyclerview.widget.AsyncListDiffer
 import androidx.recyclerview.widget.DiffUtil
 import androidx.recyclerview.widget.RecyclerView
+import org.oxycblt.auxio.util.logW
 
 /**
  * The base for all items in Auxio. Any datatype can derive this type and gain some behavior not
@@ -171,3 +172,43 @@ abstract class SimpleItemCallback<T : Item> : DiffUtil.ItemCallback<T>() {
         return oldItem.id == newItem.id
     }
 }
+
+abstract class ActivationAdapter<VH : RecyclerView.ViewHolder> : RecyclerView.Adapter<VH>() {
+    override fun onBindViewHolder(holder: VH, position: Int) = throw UnsupportedOperationException()
+
+    override fun onBindViewHolder(holder: VH, position: Int, payloads: List<Any>) {
+        holder.itemView.isActivated = shouldActivateViewHolder(position)
+    }
+
+    protected abstract fun shouldActivateViewHolder(position: Int): Boolean
+
+    protected inline fun <reified T : Item> activateImpl(
+        currentList: List<Item>,
+        oldItem: T?,
+        newItem: T?
+    ) {
+        if (oldItem != null) {
+            val pos = currentList.indexOfFirst { item -> item.id == oldItem.id && item is T }
+
+            if (pos > -1) {
+                notifyItemChanged(pos, PAYLOAD_ACTIVATION_CHANGED)
+            } else {
+                logW("oldItem was not in adapter data")
+            }
+        }
+
+        if (newItem != null) {
+            val pos = currentList.indexOfFirst { item -> item is T && item.id == newItem.id }
+
+            if (pos > -1) {
+                notifyItemChanged(pos, PAYLOAD_ACTIVATION_CHANGED)
+            } else {
+                logW("newItem was not in adapter data")
+            }
+        }
+    }
+    
+    companion object {
+        val PAYLOAD_ACTIVATION_CHANGED = Any()
+    }
+}

info/ARCHITECTURE.md

@@ -213,8 +213,7 @@ list similar to this:
 `Item being displayed | Header Item | Child Item | Child Item | Child Item...`
 
 Note that the actual dataset used is more complex once sorting and disc numbers is taken into
-account. Item highlighting and certain shared ViewHolders are already managed by the `DetailAdapter`
+account.
-super-class, which should be implemented by all adapters in the detail UI.
 
 #### `.home`
 This package contains the components for the "home" UI in Auxio, or the UI that the user first sees