Add fast scrolling to SongsFragment

Add a fast-scroll bar to the list of songs in SongsFragment.

app/build.gradle

@@ -77,16 +77,21 @@ dependencies {
 
     // --- THIRD PARTY ---
 
+    // ExoPlayer
+    def exoplayer_version = "2.12.1"
+    implementation "com.google.android.exoplayer:exoplayer-core:$exoplayer_version"
+    implementation "com.google.android.exoplayer:extension-mediasession:$exoplayer_version"
+
     // Image loading
     implementation 'io.coil-kt:coil:0.13.0'
 
     // Material
     implementation 'com.google.android.material:material:1.3.0-alpha03'
 
-    // ExoPlayer
-    def exoplayer_version = "2.12.1"
-    implementation "com.google.android.exoplayer:exoplayer-core:$exoplayer_version"
-    implementation "com.google.android.exoplayer:extension-mediasession:$exoplayer_version"
+    // Fast-Scroll [Too lazy to make it myself]
+    implementation 'com.reddit:indicator-fast-scroll:1.3.0'
+
+    // --- DEV ---
 
     // Lint
     ktlint "com.pinterest:ktlint:0.37.2"

app/src/main/java/org/oxycblt/auxio/songs/SongAdapter.kt

@@ -7,7 +7,7 @@ import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.recycler.viewholders.SongViewHolder
 
 class SongAdapter(
-    private val data: List<Song>,
+    val data: List<Song>,
     private val doOnClick: (data: Song) -> Unit,
     private val doOnLongClick: (data: Song, view: View) -> Unit
 ) : RecyclerView.Adapter<SongViewHolder>() {

app/src/main/java/org/oxycblt/auxio/songs/SongsFragment.kt

@@ -1,5 +1,6 @@
 package org.oxycblt.auxio.songs
 
+import android.content.res.ColorStateList
 import android.os.Bundle
 import android.util.Log
 import android.view.LayoutInflater
@@ -8,12 +9,17 @@ import android.view.ViewGroup
 import androidx.appcompat.widget.PopupMenu
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
+import androidx.recyclerview.widget.LinearLayoutManager
+import com.reddit.indicatorfastscroll.FastScrollItemIndicator
+import com.reddit.indicatorfastscroll.FastScrollerView
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentSongsBinding
 import org.oxycblt.auxio.music.MusicStore
 import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.playback.state.PlaybackMode
+import org.oxycblt.auxio.ui.accent
 import org.oxycblt.auxio.ui.setupSongActions
+import org.oxycblt.auxio.ui.toColor
 
 /**
  * A [Fragment] that shows a list of all songs on the device. Contains options to search/shuffle
@@ -32,8 +38,17 @@ class SongsFragment : Fragment() {
 
         val musicStore = MusicStore.getInstance()
 
+        val songAdapter = SongAdapter(
+            musicStore.songs,
+            doOnClick = { playbackModel.playSong(it, PlaybackMode.ALL_SONGS) },
+            doOnLongClick = { data, view ->
+                PopupMenu(requireContext(), view).setupSongActions(
+                    data, requireContext(), playbackModel
+                )
+            }
+        )
+
         // TODO: Add option to search songs [Or just make a dedicated tab]
-        // TODO: Fast scrolling?
 
         // --- UI SETUP ---
 
@@ -45,16 +60,75 @@ class SongsFragment : Fragment() {
         }
 
         binding.songRecycler.apply {
-            adapter = SongAdapter(
-                musicStore.songs,
-                doOnClick = { playbackModel.playSong(it, PlaybackMode.ALL_SONGS) },
-                doOnLongClick = { data, view ->
-                    PopupMenu(requireContext(), view).setupSongActions(
-                        data, requireContext(), playbackModel
+            adapter = songAdapter
+            setHasFixedSize(true)
+        }
+
+        binding.songFastScroll.apply {
+            var hasAddedNumber = false
+            var iters = 0
+
+            setupWithRecyclerView(
+                binding.songRecycler,
+                { pos ->
+                    val item = musicStore.songs[pos]
+                    iters++
+
+                    var char = item.name[0].toUpperCase()
+
+                    // If the item starts with "the"/"a", then actually use the character after that
+                    // as its initial. Yes, this is stupidly anglo-centric but the code [hopefully]
+                    // shouldn't run with other languages.
+                    if (item.name.length > 5 &&
+                        item.name.startsWith("the ", ignoreCase = true)
+                    ) {
+                        char = item.name[4].toUpperCase()
+                    } else if (item.name.length > 3 &&
+                        item.name.startsWith("a ", ignoreCase = true)
+                    ) {
+                        char = item.name[2].toUpperCase()
+                    }
+
+                    // Check if this song starts with a number, if so, then concat it with a single
+                    // "Numeric" item if haven't already.
+                    // This check only occurs on the second time the fast scroller is polled for items.
+                    if (iters >= musicStore.songs.size) {
+                        if (char.isDigit()) {
+                            if (!hasAddedNumber) {
+                                hasAddedNumber = true
+                            } else {
+                                return@setupWithRecyclerView null
+                            }
+                        }
+                    }
+
+                    FastScrollItemIndicator.Text(
+                        char.toString()
                     )
                 }
             )
-            setHasFixedSize(true)
+
+            textAppearanceRes = R.style.TextAppearance_FastScroll
+            textColor = ColorStateList.valueOf(accent.first.toColor(requireContext()))
+            useDefaultScroller = false
+
+            itemIndicatorSelectedCallbacks.add(
+                object : FastScrollerView.ItemIndicatorSelectedCallback {
+                    override fun onItemIndicatorSelected(
+                        indicator: FastScrollItemIndicator,
+                        indicatorCenterY: Int,
+                        itemPosition: Int
+                    ) {
+                        val layoutManager = binding.songRecycler.layoutManager
+                            as LinearLayoutManager
+
+                        layoutManager.scrollToPositionWithOffset(itemPosition, 0)
+                    }
+                }
+            )
+
+            binding.songFastScrollThumb.setupWithFastScroller(this)
+            binding.songFastScrollThumb.textAppearanceRes = R.style.TextAppearance_ThumbIndicator
         }
 
         Log.d(this::class.simpleName, "Fragment created.")

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

@@ -4,7 +4,7 @@
     xmlns:tools="http://schemas.android.com/tools"
     tools:context=".songs.SongsFragment">
 
-    <LinearLayout
+    <androidx.constraintlayout.widget.ConstraintLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
@@ -16,17 +16,38 @@
             android:layout_height="?android:attr/actionBarSize"
             android:background="?android:attr/windowBackground"
             android:elevation="@dimen/elevation_normal"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toTopOf="parent"
             app:menu="@menu/menu_songs"
-            app:titleTextAppearance="@style/TextAppearance.Toolbar.Header"
-            app:title="@string/label_all_songs" />
+            app:title="@string/label_all_songs"
+            app:titleTextAppearance="@style/TextAppearance.Toolbar.Header" />
 
         <androidx.recyclerview.widget.RecyclerView
             android:id="@+id/song_recycler"
-            android:layout_width="match_parent"
+            android:layout_width="0dp"
             android:layout_height="0dp"
-            android:layout_weight="1"
             app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toStartOf="@+id/song_fast_scroll"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@+id/song_toolbar"
             tools:listitem="@layout/item_song" />
 
-    </LinearLayout>
+        <com.reddit.indicatorfastscroll.FastScrollerView
+            android:id="@+id/song_fast_scroll"
+            android:layout_width="wrap_content"
+            android:layout_height="0dp"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintTop_toBottomOf="@+id/song_toolbar" />
+
+        <com.reddit.indicatorfastscroll.FastScrollerThumbView
+            android:id="@+id/song_fast_scroll_thumb"
+            android:layout_width="50dp"
+            android:layout_height="0dp"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toStartOf="@+id/song_fast_scroll"
+            app:layout_constraintTop_toBottomOf="@+id/song_toolbar" />
+
+    </androidx.constraintlayout.widget.ConstraintLayout>
 </layout>

app/src/main/res/values/styles.xml

@@ -47,6 +47,14 @@
         <item name="android:popupBackground">@color/background</item>
     </style>
 
+    <style name="TextAppearance.FastScroll" parent="TextAppearance.AppCompat.Body2">
+        <item name="android:fontFamily">@font/inter_semibold</item>
+    </style>
+
+    <style name="TextAppearance.ThumbIndicator" parent="TextAppearance.FastScroll">
+        <item name="android:textSize">18sp</item>
+    </style>
+
     <!--
     Fix to get QueueFragment to not overlap the Status Bar or Navigation Bar [Currently unused but still here]
     https://stackoverflow.com/a/57790787/14143986