home: make fab hide when fast scrolling

Hide the FAB when fast scrolling. This is just a UX enhancement.

app/src/main/java/org/oxycblt/auxio/home/HomeFragment.kt

@@ -205,6 +205,17 @@ class HomeFragment : Fragment() {
 
         // --- VIEWMODEL SETUP ---
 
+        // There is no way a fast scrolling event can continue across a re-create. Reset it.
+        homeModel.updateFastScrolling(false)
+
+        homeModel.fastScrolling.observe(viewLifecycleOwner) { scrolling ->
+            if (scrolling) {
+                binding.homeFab.hide()
+            } else {
+                binding.homeFab.show()
+            }
+        }
+
         homeModel.recreateTabs.observe(viewLifecycleOwner) { recreate ->
             // notifyDataSetChanged is not practical for recreating here since it will cache
             // the previous fragments. Just instantiate a whole new adapter.

app/src/main/java/org/oxycblt/auxio/home/HomeViewModel.kt

@@ -61,6 +61,9 @@ class HomeViewModel : ViewModel(), SettingsManager.Callback {
     private val mCurTab = MutableLiveData(tabs[0])
     val curTab: LiveData<DisplayMode> = mCurTab
 
+    private val mFastScrolling = MutableLiveData(false)
+    val fastScrolling: LiveData<Boolean> = mFastScrolling
+
     /**
      * Marker to recreate all library tabs, usually initiated by a settings change.
      * When this flag is set, all tabs (and their respective viewpager fragments) will be
@@ -123,6 +126,14 @@ class HomeViewModel : ViewModel(), SettingsManager.Callback {
         }
     }
 
+    /**
+     * Update the fast scroll state. This is used to control the FAB visibility whenever
+     * the user begins to fast scroll.
+     */
+    fun updateFastScrolling(scrolling: Boolean) {
+        mFastScrolling.value = scrolling
+    }
+
     // --- OVERRIDES ---
 
     override fun onLibTabsUpdate(libTabs: Array<Tab>) {

app/src/main/java/org/oxycblt/auxio/home/fastscroll/FastScrollRecyclerView.kt

@@ -62,6 +62,7 @@ import kotlin.math.abs
  * - Track view is now only used for touch bounds
  * - Redundant functions have been merged
  * - Variable names are no longer prefixed with m
+ * - Added drag listener
  * - TODO: Added documentation
  * - TODO: Popup will center itself to the thumb when possible
  *
@@ -72,7 +73,8 @@ class FastScrollRecyclerView @JvmOverloads constructor(
     attrs: AttributeSet? = null,
     defStyleAttr: Int = -1
 ) : RecyclerView(context, attrs, defStyleAttr) {
-    private var popupProvider: ((Int) -> String)? = null
+    var popupProvider: ((Int) -> String)? = null
+    var onDragListener: ((Boolean) -> Unit)? = null
 
     private val minTouchTargetSize: Int = resources.getDimensionPixelSize(R.dimen.size_btn_small)
     private val touchSlop: Int = ViewConfiguration.get(context).scaledTouchSlop
@@ -191,7 +193,7 @@ class FastScrollRecyclerView @JvmOverloads constructor(
         })
     }
 
-    fun setup(provider: (Int) -> String) {
+    fun addPopupProvider(provider: (Int) -> String) {
         popupProvider = provider
     }
 
@@ -496,6 +498,7 @@ class FastScrollRecyclerView @JvmOverloads constructor(
         }
 
         this.dragging = dragging
+
         if (this.dragging) {
             parent.requestDisallowInterceptTouchEvent(true)
         }
@@ -511,6 +514,8 @@ class FastScrollRecyclerView @JvmOverloads constructor(
             postAutoHideScrollbar()
             hidePopup()
         }
+
+        onDragListener?.invoke(dragging)
     }
 
     // --- SCROLLBAR APPEARANCE ---

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

@@ -51,7 +51,10 @@ abstract class HomeListFragment : Fragment() {
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
 
-        binding.homeRecycler.setup(popupProvider)
+        binding.homeRecycler.popupProvider = popupProvider
+        binding.homeRecycler.onDragListener = { dragging ->
+            homeModel.updateFastScrolling(dragging)
+        }
     }
 
     protected fun <T : BaseModel, VH : RecyclerView.ViewHolder> setupRecycler(

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

@@ -8,7 +8,6 @@
         android:id="@+id/main_layout"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:animateLayoutChanges="true"
         android:orientation="vertical">
 
         <org.oxycblt.auxio.ui.LiftAppBarLayout