list: tweak header/divider object hierarchy

Make a new generic Header/Divider superclass that all
headers derive.

This allows disc headers to be recognized generically
in places like the grid layout manager.

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

@@ -31,10 +31,10 @@ import kotlin.math.min
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentDetailBinding
 import org.oxycblt.auxio.detail.list.DetailListAdapter
-import org.oxycblt.auxio.list.Divider
-import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.ListFragment
 import org.oxycblt.auxio.list.ListViewModel
+import org.oxycblt.auxio.list.PlainDivider
+import org.oxycblt.auxio.list.PlainHeader
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.MusicViewModel
@@ -91,7 +91,7 @@ abstract class DetailFragment<P : MusicParent, C : Music> :
                         detailModel.artistSongList.value.getOrElse(it - 1) {
                             return@setFullWidthLookup false
                         }
-                    item is Divider || item is Header
+                    item is PlainDivider || item is PlainHeader
                 } else {
                     true
                 }

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

@@ -34,10 +34,10 @@ import org.oxycblt.auxio.detail.list.DiscHeader
 import org.oxycblt.auxio.detail.list.EditHeader
 import org.oxycblt.auxio.detail.list.SortHeader
 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.ListSettings
+import org.oxycblt.auxio.list.PlainDivider
+import org.oxycblt.auxio.list.PlainHeader
 import org.oxycblt.auxio.list.adapter.UpdateInstructions
 import org.oxycblt.auxio.list.sort.Sort
 import org.oxycblt.auxio.music.Album
@@ -531,7 +531,7 @@ constructor(
         list: MutableStateFlow<List<Item>>,
         instructions: MutableEvent<UpdateInstructions>,
         replace: Int?,
-        songHeader: (Int) -> Header = { SortHeader(it) }
+        songHeader: (Int) -> PlainHeader = { SortHeader(it) }
     ) {
         if (detail == null) {
             parent.value = null
@@ -547,7 +547,7 @@ constructor(
                             if (section is DetailSection.Songs) songHeader(section.stringRes)
                             else BasicHeader(section.stringRes)
                         if (newList.isNotEmpty()) {
-                            newList.add(Divider(header))
+                            newList.add(PlainDivider(header))
                         }
                         newList.add(header)
                         section.items
@@ -555,7 +555,7 @@ constructor(
                     is DetailSection.Discs -> {
                         val header = SortHeader(section.stringRes)
                         if (newList.isNotEmpty()) {
-                            newList.add(Divider(header))
+                            newList.add(PlainDivider(header))
                         }
                         newList.add(header)
                         buildList<Item> {
@@ -600,7 +600,7 @@ constructor(
         val list = mutableListOf<Item>()
         if (edited.isNotEmpty()) {
             val header = EditHeader(R.string.lbl_songs)
-            list.add(Divider(header))
+            list.add(PlainDivider(header))
             list.add(header)
             list.addAll(edited)
         }

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

@@ -29,6 +29,8 @@ import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.ItemAlbumSongBinding
 import org.oxycblt.auxio.databinding.ItemDiscHeaderBinding
+import org.oxycblt.auxio.list.Divider
+import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.SelectableListListener
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
@@ -100,9 +102,9 @@ class AlbumDetailListAdapter(private val listener: Listener<Song>) :
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
-data class DiscHeader(val inner: Disc?) : Item
+data class DiscHeader(val inner: Disc?) : Header
 
-data class DiscDivider(val anchor: DiscHeader?) : Item
+data class DiscDivider(override val anchor: DiscHeader?) : Divider<DiscHeader>
 
 /**
  * A [RecyclerView.ViewHolder] that displays a [DiscHeader] to delimit different disc groups. Use

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

@@ -27,9 +27,9 @@ 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.PlainDivider
+import org.oxycblt.auxio.list.PlainHeader
 import org.oxycblt.auxio.list.SelectableListListener
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.adapter.SimpleDiffCallback
@@ -55,7 +55,7 @@ abstract class DetailListAdapter(
     override fun getItemViewType(position: Int) =
         when (getItem(position)) {
             // Implement support for headers and sort headers
-            is Divider -> DividerViewHolder.VIEW_TYPE
+            is PlainDivider -> DividerViewHolder.VIEW_TYPE
             is BasicHeader -> BasicHeaderViewHolder.VIEW_TYPE
             is SortHeader -> SortHeaderViewHolder.VIEW_TYPE
             else -> super.getItemViewType(position)
@@ -91,7 +91,7 @@ abstract class DetailListAdapter(
             object : SimpleDiffCallback<Item>() {
                 override fun areContentsTheSame(oldItem: Item, newItem: Item): Boolean {
                     return when {
-                        oldItem is Divider && newItem is Divider ->
+                        oldItem is PlainDivider && newItem is PlainDivider ->
                             DividerViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is BasicHeader && newItem is BasicHeader ->
                             BasicHeaderViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
@@ -110,7 +110,7 @@ abstract class DetailListAdapter(
  * @param titleRes The string resource to use as the header title
  * @author Alexander Capehart (OxygenCobalt)
  */
-data class SortHeader(@StringRes override val titleRes: Int) : Header
+data class SortHeader(@StringRes override val titleRes: Int) : PlainHeader
 
 /**
  * A [RecyclerView.ViewHolder] that displays a [SortHeader] and it's actions. Use [from] to create

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

@@ -33,8 +33,8 @@ import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.databinding.ItemEditHeaderBinding
 import org.oxycblt.auxio.databinding.ItemEditableSongBinding
 import org.oxycblt.auxio.list.EditableListListener
-import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.Item
+import org.oxycblt.auxio.list.PlainHeader
 import org.oxycblt.auxio.list.adapter.PlayingIndicatorAdapter
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.adapter.SimpleDiffCallback
@@ -140,12 +140,12 @@ class PlaylistDetailListAdapter(private val listener: Listener) :
 }
 
 /**
- * A [Header] variant that displays an edit button.
+ * A [PlainHeader] variant that displays an edit button.
  *
  * @param titleRes The string resource to use as the header title
  * @author Alexander Capehart (OxygenCobalt)
  */
-data class EditHeader(@StringRes override val titleRes: Int) : Header
+data class EditHeader(@StringRes override val titleRes: Int) : PlainHeader
 
 /**
  * Displays an [EditHeader] and it's actions. Use [from] to create an instance.

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

@@ -24,12 +24,14 @@ import androidx.annotation.StringRes
 /** A marker for something that is a RecyclerView item. Has no functionality on it's own. */
 interface Item
 
+interface Header : Item
+
 /**
  * A "header" used for delimiting groups of data.
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
-interface Header : Item {
+interface PlainHeader : Header {
     /** The string resource used for the header's title. */
     val titleRes: Int
 }
@@ -40,12 +42,16 @@ interface Header : Item {
  * @param titleRes The string resource used for the header's title.
  * @author Alexander Capehart (OxygenCobalt)
  */
-data class BasicHeader(@StringRes override val titleRes: Int) : Header
+data class BasicHeader(@StringRes override val titleRes: Int) : PlainHeader
+
+interface Divider<T> : Item {
+    val anchor: T?
+}
 
 /**
  * A divider decoration used to delimit groups of data.
  *
- * @param anchor The [Header] this divider should be next to in a list. Used as a way to preserve
+ * @param anchor The [PlainHeader] this divider should be next to in a list. Used as a way to
- *   divider continuity during list updates.
+ *   preserve divider continuity during list updates.
  */
-data class Divider(val anchor: Header?) : Item
+data class PlainDivider(override val anchor: PlainHeader?) : Divider<PlainHeader>

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

@@ -27,7 +27,7 @@ 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.PlainDivider
 import org.oxycblt.auxio.list.SelectableListListener
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.adapter.SimpleDiffCallback
@@ -360,7 +360,7 @@ class BasicHeaderViewHolder private constructor(private val binding: ItemHeaderB
 }
 
 /**
- * A [RecyclerView.ViewHolder] that displays a [Divider]. Use [from] to create an instance.
+ * A [RecyclerView.ViewHolder] that displays a [PlainDivider]. Use [from] to create an instance.
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
@@ -381,8 +381,8 @@ class DividerViewHolder private constructor(divider: MaterialDivider) :
 
         /** A comparator that can be used with DiffUtil. */
         val DIFF_CALLBACK =
-            object : SimpleDiffCallback<Divider>() {
+            object : SimpleDiffCallback<PlainDivider>() {
-                override fun areContentsTheSame(oldItem: Divider, newItem: Divider) =
+                override fun areContentsTheSame(oldItem: PlainDivider, newItem: PlainDivider) =
                     oldItem.anchor == newItem.anchor
             }
     }

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

@@ -21,8 +21,8 @@ package org.oxycblt.auxio.search
 import android.view.ViewGroup
 import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.list.BasicHeader
-import org.oxycblt.auxio.list.Divider
 import org.oxycblt.auxio.list.Item
+import org.oxycblt.auxio.list.PlainDivider
 import org.oxycblt.auxio.list.SelectableListListener
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.adapter.SimpleDiffCallback
@@ -57,7 +57,7 @@ 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 PlainDivider -> DividerViewHolder.VIEW_TYPE
             is BasicHeader -> BasicHeaderViewHolder.VIEW_TYPE
             else -> super.getItemViewType(position)
         }
@@ -102,7 +102,7 @@ class SearchAdapter(private val listener: SelectableListListener<Music>) :
                             GenreViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is Playlist && newItem is Playlist ->
                             PlaylistViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
-                        oldItem is Divider && newItem is Divider ->
+                        oldItem is PlainDivider && newItem is PlainDivider ->
                             DividerViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is BasicHeader && newItem is BasicHeader ->
                             BasicHeaderViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)

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

@@ -38,11 +38,11 @@ import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentSearchBinding
 import org.oxycblt.auxio.detail.DetailViewModel
 import org.oxycblt.auxio.detail.Show
-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.ListViewModel
+import org.oxycblt.auxio.list.PlainDivider
+import org.oxycblt.auxio.list.PlainHeader
 import org.oxycblt.auxio.list.menu.Menu
 import org.oxycblt.auxio.music.Album
 import org.oxycblt.auxio.music.Artist
@@ -153,7 +153,7 @@ class SearchFragment : ListFragment<Music, FragmentSearchBinding>() {
                     searchModel.searchResults.value.getOrElse(it) {
                         return@setFullWidthLookup false
                     }
-                item is Divider || item is Header
+                item is PlainDivider || item is PlainHeader
             }
         }
 

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

@@ -30,8 +30,8 @@ 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.PlainDivider
 import org.oxycblt.auxio.list.sort.Sort
 import org.oxycblt.auxio.music.MusicRepository
 import org.oxycblt.auxio.music.MusicType
@@ -152,7 +152,7 @@ constructor(
                 logD("Adding ${it.size} albums to search results")
                 val header = BasicHeader(R.string.lbl_albums)
                 if (isNotEmpty()) {
-                    add(Divider(header))
+                    add(PlainDivider(header))
                 }
 
                 add(header)
@@ -162,7 +162,7 @@ constructor(
                 logD("Adding ${it.size} playlists to search results")
                 val header = BasicHeader(R.string.lbl_playlists)
                 if (isNotEmpty()) {
-                    add(Divider(header))
+                    add(PlainDivider(header))
                 }
 
                 add(header)
@@ -172,7 +172,7 @@ constructor(
                 logD("Adding ${it.size} genres to search results")
                 val header = BasicHeader(R.string.lbl_genres)
                 if (isNotEmpty()) {
-                    add(Divider(header))
+                    add(PlainDivider(header))
                 }
 
                 add(header)
@@ -182,7 +182,7 @@ constructor(
                 logD("Adding ${it.size} songs to search results")
                 val header = BasicHeader(R.string.lbl_songs)
                 if (isNotEmpty()) {
-                    add(Divider(header))
+                    add(PlainDivider(header))
                 }
 
                 add(header)