Fix bugs with Queue

- Fix a bug where the queue would scroll up when the player moved to another song.
- Fix bug where queue would show even with no songs.
- Fix a crash from removing the last song of a queue.

app/src/main/java/org/oxycblt/auxio/playback/NotificationUtils.kt

@@ -145,7 +145,8 @@ private fun newAction(action: String, context: Context): NotificationCompat.Acti
         NotificationUtils.ACTION_SKIP_NEXT -> R.drawable.ic_skip_next
 
         NotificationUtils.ACTION_EXIT -> R.drawable.ic_exit
-        else -> R.drawable.ic_play
+
+        else -> R.drawable.ic_error
     }
 
     return NotificationCompat.Action.Builder(

app/src/main/java/org/oxycblt/auxio/playback/PlaybackFragment.kt

@@ -5,6 +5,7 @@ import android.graphics.drawable.AnimatedVectorDrawable
 import android.os.Bundle
 import android.util.Log
 import android.view.LayoutInflater
+import android.view.MenuItem
 import android.view.View
 import android.view.ViewGroup
 import android.widget.SeekBar
@@ -46,6 +47,17 @@ class PlaybackFragment : Fragment(), SeekBar.OnSeekBarChangeListener {
             requireContext(), R.drawable.ic_play_to_pause
         ) as AnimatedVectorDrawable
 
+        // Can't set the tint of a MenuItem below Android 8, so use icons instead.
+        val iconQueueActive = ContextCompat.getDrawable(
+            requireContext(), R.drawable.ic_queue
+        )
+
+        val iconQueueInactive = ContextCompat.getDrawable(
+            requireContext(), R.drawable.ic_queue_inactive
+        )
+
+        val queueMenuItem: MenuItem
+
         // --- UI SETUP ---
 
         binding.lifecycleOwner = viewLifecycleOwner
@@ -64,6 +76,8 @@ class PlaybackFragment : Fragment(), SeekBar.OnSeekBarChangeListener {
 
                 true
             }
+
+            queueMenuItem = menu.findItem(R.id.action_queue)
         }
 
         // Make marquee scroll work
@@ -163,6 +177,17 @@ class PlaybackFragment : Fragment(), SeekBar.OnSeekBarChangeListener {
             }
         }
 
+        playbackModel.nextItemsInQueue.observe(viewLifecycleOwner) {
+            // Disable the option to open the queue if there's nothing in it.
+            if (it.isEmpty()) {
+                queueMenuItem.isEnabled = false
+                queueMenuItem.icon = iconQueueInactive
+            } else {
+                queueMenuItem.isEnabled = true
+                queueMenuItem.icon = iconQueueActive
+            }
+        }
+
         Log.d(this::class.simpleName, "Fragment Created.")
 
         return binding.root

app/src/main/java/org/oxycblt/auxio/playback/PlaybackService.kt

@@ -39,12 +39,11 @@ import org.oxycblt.auxio.music.coil.getBitmap
 import org.oxycblt.auxio.music.toURI
 import org.oxycblt.auxio.playback.state.LoopMode
 import org.oxycblt.auxio.playback.state.PlaybackMode
-import org.oxycblt.auxio.playback.state.PlaybackStateCallback
 import org.oxycblt.auxio.playback.state.PlaybackStateManager
 
 // A Service that manages the single ExoPlayer instance and manages the system-side
 // aspects of playback.
-class PlaybackService : Service(), Player.EventListener, PlaybackStateCallback {
+class PlaybackService : Service(), Player.EventListener, PlaybackStateManager.Callback {
     private val player: SimpleExoPlayer by lazy {
         SimpleExoPlayer.Builder(applicationContext).build()
     }

app/src/main/java/org/oxycblt/auxio/playback/PlaybackViewModel.kt

@@ -12,13 +12,12 @@ import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.music.toDuration
 import org.oxycblt.auxio.playback.state.LoopMode
 import org.oxycblt.auxio.playback.state.PlaybackMode
-import org.oxycblt.auxio.playback.state.PlaybackStateCallback
 import org.oxycblt.auxio.playback.state.PlaybackStateManager
 
 // A ViewModel that acts as an intermediary between the UI and PlaybackStateManager
 // TODO: Implement User Queue
 // TODO: Implement Persistence through a Database
-class PlaybackViewModel : ViewModel(), PlaybackStateCallback {
+class PlaybackViewModel : ViewModel(), PlaybackStateManager.Callback {
     // Playback
     private val mSong = MutableLiveData<Song?>()
     val song: LiveData<Song?> get() = mSong
@@ -59,7 +58,6 @@ class PlaybackViewModel : ViewModel(), PlaybackStateCallback {
         it.slice((mIndex.value!! + 1) until it.size)
     }
 
-    // Service setup
     private val playbackManager = PlaybackStateManager.getInstance()
 
     init {

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueFragment.kt

@@ -7,6 +7,7 @@ import android.view.ViewGroup
 import androidx.fragment.app.activityViewModels
 import androidx.recyclerview.widget.DefaultItemAnimator
 import androidx.recyclerview.widget.ItemTouchHelper
+import androidx.recyclerview.widget.LinearLayoutManager
 import com.google.android.material.bottomsheet.BottomSheetDialogFragment
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentQueueBinding
@@ -47,11 +48,24 @@ class QueueFragment : BottomSheetDialogFragment() {
         // --- VIEWMODEL SETUP ---
 
         playbackModel.nextItemsInQueue.observe(viewLifecycleOwner) {
+            if (it.isEmpty()) {
+                dismiss()
+
+                return@observe
+            }
+
             // If the first item is being moved, then scroll to the top position on completion
             // to prevent ListAdapter from scrolling uncontrollably.
             if (queueAdapter.currentList.isNotEmpty() && it[0].id != queueAdapter.currentList[0].id) {
                 queueAdapter.submitList(it.toMutableList()) {
-                    binding.queueRecycler.scrollToPosition(0)
+                    // Make sure that the RecyclerView doesn't scroll to the top if the first item
+                    // changed, but is not visible.
+                    val firstItem = (binding.queueRecycler.layoutManager as LinearLayoutManager)
+                        .findFirstVisibleItemPosition()
+
+                    if (firstItem == -1 || firstItem == 0) {
+                        binding.queueRecycler.scrollToPosition(0)
+                    }
                 }
             } else {
                 queueAdapter.submitList(it.toMutableList())

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateCallback.kt

@@ -1,17 +0,0 @@
-package org.oxycblt.auxio.playback.state
-
-import org.oxycblt.auxio.music.Song
-
-interface PlaybackStateCallback {
-    fun onSongUpdate(song: Song?) {}
-    fun onPositionUpdate(position: Long) {}
-    fun onQueueUpdate(queue: MutableList<Song>) {}
-    fun onModeUpdate(mode: PlaybackMode) {}
-    fun onIndexUpdate(index: Int) {}
-    fun onPlayingUpdate(isPlaying: Boolean) {}
-    fun onShuffleUpdate(isShuffling: Boolean) {}
-    fun onLoopUpdate(mode: LoopMode) {}
-
-    // Service callbacks
-    fun onSeekConfirm(position: Long) {}
-}

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateManager.kt

@@ -77,13 +77,13 @@ class PlaybackStateManager private constructor() {
 
     // --- CALLBACKS ---
 
-    private val callbacks = mutableListOf<PlaybackStateCallback>()
+    private val callbacks = mutableListOf<Callback>()
 
-    fun addCallback(callback: PlaybackStateCallback) {
+    fun addCallback(callback: Callback) {
         callbacks.add(callback)
     }
 
-    fun removeCallback(callback: PlaybackStateCallback) {
+    fun removeCallback(callback: Callback) {
         callbacks.remove(callback)
     }
 
@@ -397,4 +397,16 @@ class PlaybackStateManager private constructor() {
             }
         }
     }
+
+    interface Callback {
+        fun onSongUpdate(song: Song?) {}
+        fun onPositionUpdate(position: Long) {}
+        fun onQueueUpdate(queue: MutableList<Song>) {}
+        fun onModeUpdate(mode: PlaybackMode) {}
+        fun onIndexUpdate(index: Int) {}
+        fun onPlayingUpdate(isPlaying: Boolean) {}
+        fun onShuffleUpdate(isShuffling: Boolean) {}
+        fun onLoopUpdate(mode: LoopMode) {}
+        fun onSeekConfirm(position: Long) {}
+    }
 }

app/src/main/res/drawable/ic_queue_inactive.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="@color/inactive_color">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M15,6L3,6v2h12L15,6zM15,10L3,10v2h12v-2zM3,16h8v-2L3,14v2zM17,6v8.18c-0.31,-0.11 -0.65,-0.18 -1,-0.18 -1.66,0 -3,1.34 -3,3s1.34,3 3,3 3,-1.34 3,-3L19,8h3L22,6h-5z" />
+</vector>