Improve queue editing

Fix issue where moving queue items would swap them, not move them, also prevent QueueAdapter from scrolling uncontrollably if the first item is moved.

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

@@ -255,7 +255,8 @@ class PlaybackViewModel : ViewModel() {
         mCanAnimate = false
     }
 
-    // Move two queue items. Called by QueueDragCallback.
+    // Move two queue items. Note that this function does not force-update the queue,
+    // as calling updateData with a drag would cause bugs.
     fun moveQueueItems(adapterFrom: Int, adapterTo: Int) {
         // Translate the adapter indices into the correct queue indices
         val delta = mQueue.value!!.size - formattedQueue.value!!.size
@@ -265,13 +266,11 @@ class PlaybackViewModel : ViewModel() {
 
         try {
             val currentItem = mQueue.value!![from]
-            val targetItem = mQueue.value!![to]
 
-            // Then swap the items manually since kotlin does have a swap function.
-            mQueue.value!![to] = currentItem
-            mQueue.value!![from] = targetItem
+            mQueue.value!!.removeAt(from)
+            mQueue.value!!.add(to, currentItem)
         } catch (exception: IndexOutOfBoundsException) {
-            Log.e(this::class.simpleName, "Indices were out of bounds, did not swap queue items")
+            Log.e(this::class.simpleName, "Indices were out of bounds, did not move queue item")
 
             return
         }
@@ -279,7 +278,8 @@ class PlaybackViewModel : ViewModel() {
         forceQueueUpdate()
     }
 
-    // Remove a queue item. Called by QueueDragCallback.
+    // Remove a queue item. Note that this function does not force-update the queue,
+    // as calling updateData with a drag would cause bugs.
     fun removeQueueItem(adapterIndex: Int) {
         // Translate the adapter index into the correct queue index
         val delta = mQueue.value!!.size - formattedQueue.value!!.size

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

@@ -11,10 +11,9 @@ import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.recycler.DiffCallback
 import org.oxycblt.auxio.recycler.viewholders.BaseViewHolder
 
-// FIXME: Build a Diff function so that QueueAdapter doesn't scroll wildly when things are moved
-class QueueAdapter(private val dragCallback: ItemTouchHelper) :
-    ListAdapter<Song, QueueAdapter.ViewHolder>(DiffCallback<Song>()) {
-
+class QueueAdapter(
+    val touchHelper: ItemTouchHelper
+) : ListAdapter<Song, QueueAdapter.ViewHolder>(DiffCallback<Song>()) {
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
         return ViewHolder(ItemQueueSongBinding.inflate(LayoutInflater.from(parent.context)))
     }
@@ -23,7 +22,7 @@ class QueueAdapter(private val dragCallback: ItemTouchHelper) :
         holder.bind(getItem(position))
     }
 
-    // Generic ViewHolder for a detail album
+    // Generic ViewHolder for a queue item
     inner class ViewHolder(
         private val binding: ItemQueueSongBinding,
     ) : BaseViewHolder<Song>(binding, null) {
@@ -35,7 +34,7 @@ class QueueAdapter(private val dragCallback: ItemTouchHelper) :
                 binding.songDragHandle.performClick()
 
                 if (motionEvent.actionMasked == MotionEvent.ACTION_DOWN) {
-                    dragCallback.startDrag(this)
+                    touchHelper.startDrag(this)
                     return@setOnTouchListener true
                 }
 

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

@@ -4,14 +4,17 @@ import androidx.recyclerview.widget.ItemTouchHelper
 import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.playback.PlaybackViewModel
 import kotlin.math.abs
+import kotlin.math.max
 import kotlin.math.min
 import kotlin.math.sign
 
-class QueueDragCallback(private val playbackModel: PlaybackViewModel) :
-    ItemTouchHelper.SimpleCallback(
-        ItemTouchHelper.UP or ItemTouchHelper.DOWN,
-        ItemTouchHelper.START
-    ) {
+// The drag callback used for the Queue RecyclerView.
+class QueueDragCallback(
+    private val playbackModel: PlaybackViewModel
+) : ItemTouchHelper.SimpleCallback(
+    ItemTouchHelper.UP or ItemTouchHelper.DOWN,
+    ItemTouchHelper.START
+) {
     override fun interpolateOutOfBoundsScroll(
         recyclerView: RecyclerView,
         viewSize: Int,
@@ -19,11 +22,14 @@ class QueueDragCallback(private val playbackModel: PlaybackViewModel) :
         totalSize: Int,
         msSinceStartScroll: Long
     ): Int {
+        // Fix to make QueueFragment scroll when an item is scrolled out of bounds.
+        // Adapted from NewPipe: https://github.com/TeamNewPipe/NewPipe
+
         val standardSpeed = super.interpolateOutOfBoundsScroll(
             recyclerView, viewSize, viewSizeOutOfBounds, totalSize, msSinceStartScroll
         )
 
-        val clampedAbsVelocity = Math.max(
+        val clampedAbsVelocity = max(
             MINIMUM_INITIAL_DRAG_VELOCITY,
             min(
                 abs(standardSpeed),

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

@@ -27,8 +27,9 @@ class QueueFragment : BottomSheetDialogFragment() {
     ): View? {
         val binding = FragmentQueueBinding.inflate(inflater)
 
-        val helper = ItemTouchHelper(QueueDragCallback(playbackModel))
-
+        val helper = ItemTouchHelper(
+            QueueDragCallback(playbackModel)
+        )
         val queueAdapter = QueueAdapter(helper)
 
         // --- UI SETUP ---
@@ -36,9 +37,9 @@ class QueueFragment : BottomSheetDialogFragment() {
         binding.queueHeader.setTextColor(accent.first.toColor(requireContext()))
         binding.queueRecycler.apply {
             adapter = queueAdapter
+            itemAnimator = DefaultItemAnimator()
             applyDivider()
             setHasFixedSize(true)
-            itemAnimator = DefaultItemAnimator()
 
             helper.attachToRecyclerView(this)
         }
@@ -46,7 +47,15 @@ class QueueFragment : BottomSheetDialogFragment() {
         // --- VIEWMODEL SETUP ---
 
         playbackModel.formattedQueue.observe(viewLifecycleOwner) {
-            queueAdapter.submitList(it.toMutableList())
+            // 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)
+                }
+            } else {
+                queueAdapter.submitList(it.toMutableList())
+            }
         }
 
         return binding.root

app/src/main/java/org/oxycblt/auxio/recycler/viewholders/BaseViewHolder.kt

@@ -10,6 +10,7 @@ abstract class BaseViewHolder<T : BaseModel>(
     private val doOnClick: ((T) -> Unit)?
 ) : RecyclerView.ViewHolder(baseBinding.root) {
     init {
+        // Force the layout to *actually* be the screen width
         baseBinding.root.layoutParams = RecyclerView.LayoutParams(
             RecyclerView.LayoutParams.MATCH_PARENT, RecyclerView.LayoutParams.WRAP_CONTENT
         )

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

@@ -66,11 +66,12 @@
         <ImageView
             android:id="@+id/song_drag_handle"
             android:layout_width="wrap_content"
-            android:layout_height="wrap_content"
-            android:src="@drawable/ic_handle"
+            android:layout_height="0dp"
+            android:padding="@dimen/padding_small"
             android:clickable="true"
             android:focusable="true"
-            app:layout_constraintBottom_toBottomOf="parent"
+            android:src="@drawable/ic_handle"
+            app:layout_constraintBottom_toBottomOf="@+id/song_info"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintTop_toTopOf="parent"
             tools:ignore="ContentDescription" />