music: rework loading ui flow

Rework the UI flow for music loading to be more coherent with runtime
rescanning.

The loading progress is now shown as a card on the bottom of the
screen. This way, app use is not completely crippled when the app has
to rescan the music library, albeit the shuffle button still has to
be disabled during this period.

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

@@ -98,7 +98,7 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
 
                 binding.homeToolbar.alpha = 1f - (abs(offset.toFloat()) / (range.toFloat() / 2))
 
-                binding.homeContent.updatePadding(
+                binding.homePager.updatePadding(
                     bottom = binding.homeAppbar.totalScrollRange + offset)
             }
         }
@@ -107,7 +107,7 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
 
         updateTabConfiguration()
 
-        binding.homeIndexingContainer.setOnApplyWindowInsetsListener { view, insets ->
+        binding.homeIndexingWrapper.setOnApplyWindowInsetsListener { view, insets ->
             view.updatePadding(bottom = insets.systemBarInsetsCompat.bottom)
             insets
         }
@@ -141,7 +141,7 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
 
         // --- VIEWMODEL SETUP ---
 
-        collect(homeModel.isFastScrolling, ::updateFastScrolling)
+        collect(homeModel.isFastScrolling) { updateFab() }
         collect(homeModel.recreateTabs, ::handleRecreateTabs)
         collectImmediately(homeModel.currentTab, ::updateCurrentTab)
         collectImmediately(indexerModel.state, ::handleIndexerState)
@@ -190,23 +190,6 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
         return true
     }
 
-    private fun updateFastScrolling(isFastScrolling: Boolean) {
-        val binding = requireBinding()
-
-        // Make sure an update here doesn't mess up the FAB state when it comes to the
-        // loader response.
-        val state = indexerModel.state.value
-        if (!(state is Indexer.State.Complete && state.response is Indexer.Response.Ok)) {
-            return
-        }
-
-        if (isFastScrolling) {
-            binding.homeFab.hide()
-        } else {
-            binding.homeFab.show()
-        }
-    }
-
     private fun updateCurrentTab(tab: DisplayMode) {
         // Make sure that we update the scrolling view and allowed menu items whenever
         // the tab changes.
@@ -274,27 +257,23 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
 
     private fun handleIndexerState(state: Indexer.State?) {
         val binding = requireBinding()
-
         when (state) {
             is Indexer.State.Complete -> handleIndexerResponse(binding, state.response)
             is Indexer.State.Indexing -> handleIndexingState(binding, state.indexing)
             null -> {
                 logD("Indexer is in indeterminate state")
-                binding.homeFab.hide()
                 binding.homeIndexingContainer.visibility = View.INVISIBLE
-                binding.homePager.visibility = View.INVISIBLE
             }
         }
+
+        updateFab()
     }
 
     private fun handleIndexerResponse(binding: FragmentHomeBinding, response: Indexer.Response) {
         if (response is Indexer.Response.Ok) {
             binding.homeFab.show()
             binding.homeIndexingContainer.visibility = View.INVISIBLE
-            binding.homePager.visibility = View.VISIBLE
         } else {
-            binding.homeFab.hide()
-            binding.homePager.visibility = View.INVISIBLE
             binding.homeIndexingContainer.visibility = View.VISIBLE
 
             logD("Received non-ok response $response")
@@ -336,8 +315,7 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
     }
 
     private fun handleIndexingState(binding: FragmentHomeBinding, indexing: Indexer.Indexing) {
-        binding.homeFab.hide()
-        binding.homePager.visibility = View.INVISIBLE
+        updateFab()
         binding.homeIndexingContainer.visibility = View.VISIBLE
         binding.homeIndexingProgress.visibility = View.VISIBLE
         binding.homeIndexingAction.visibility = View.INVISIBLE
@@ -359,6 +337,18 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
         }
     }
 
+    private fun updateFab() {
+        val binding = requireBinding()
+        val fastScrolling = homeModel.isFastScrolling.value
+        val state = indexerModel.state.value
+        if (fastScrolling ||
+            !(state is Indexer.State.Complete && state.response is Indexer.Response.Ok)) {
+            binding.homeFab.hide()
+        } else {
+            binding.homeFab.show()
+        }
+    }
+
     private fun handleNavigation(item: Music?) {
         // Note: You will want to add a post call to this if you want to re-introduce a collapsing
         // toolbar.

app/src/main/java/org/oxycblt/auxio/music/Indexer.kt

@@ -23,6 +23,7 @@ import android.content.pm.PackageManager
 import android.database.Cursor
 import android.os.Build
 import androidx.core.content.ContextCompat
+import kotlin.coroutines.cancellation.CancellationException
 import org.oxycblt.auxio.BuildConfig
 import org.oxycblt.auxio.music.backend.Api21MediaStoreBackend
 import org.oxycblt.auxio.music.backend.Api29MediaStoreBackend
@@ -121,7 +122,7 @@ class Indexer {
         this.callback = null
     }
 
-    fun index(context: Context) {
+    suspend fun index(context: Context) {
         val generation = synchronized(this) { ++currentGeneration }
 
         val notGranted =
@@ -181,7 +182,9 @@ class Indexer {
     @Synchronized
     private fun emitIndexing(indexing: Indexing?, generation: Long) {
         if (currentGeneration != generation) {
-            return
+            // Not the running task anymore, cancel this co-routine
+            // We do this instead of using yield since it is *far* cheaper.
+            throw CancellationException()
         }
 
         indexingState = indexing
@@ -198,7 +201,9 @@ class Indexer {
     @Synchronized
     private fun emitCompletion(response: Response, generation: Long) {
         if (currentGeneration != generation) {
-            return
+            // Not the running task anymore, cancel this co-routine
+            // We do this instead of using yield since it is *far* cheaper.
+            throw CancellationException()
         }
 
         lastResponse = response

app/src/main/java/org/oxycblt/auxio/music/IndexerService.kt

@@ -46,8 +46,6 @@ import org.oxycblt.auxio.util.logD
  * @author OxygenCobalt
  *
  * TODO: Add file observing
- *
- * TODO: Rework UI flow once again
  */
 class IndexerService : Service(), Indexer.Controller, Settings.Callback {
     private val indexer = Indexer.getInstance()

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

@@ -29,60 +29,72 @@
 
     </org.oxycblt.auxio.ui.coordinator.EdgeAppBarLayout>
 
-    <FrameLayout
-        android:id="@+id/home_content"
+    <androidx.viewpager2.widget.ViewPager2
+        android:id="@+id/home_pager"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        app:layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior">
+        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
+        app:layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior"
+        tools:layout="@layout/fragment_home_list" />
 
-        <androidx.constraintlayout.widget.ConstraintLayout
+    <FrameLayout
+        android:id="@+id/home_indexing_wrapper"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_gravity="bottom"
+        android:animateLayoutChanges="true"
+        android:clipToPadding="false">
+
+        <com.google.android.material.card.MaterialCardView
             android:id="@+id/home_indexing_container"
             android:layout_width="match_parent"
-            android:layout_height="match_parent"
-            android:animateLayoutChanges="true"
-            android:paddingStart="@dimen/spacing_medium"
-            android:paddingEnd="@dimen/spacing_medium">
+            android:layout_height="wrap_content"
+            android:layout_margin="@dimen/spacing_medium">
 
-            <TextView
-                android:id="@+id/home_indexing_status"
+            <androidx.constraintlayout.widget.ConstraintLayout
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
-                android:layout_marginBottom="@dimen/spacing_medium"
-                android:gravity="center"
-                android:textAppearance="@style/TextAppearance.Auxio.BodyLarge"
-                app:layout_constraintBottom_toTopOf="@+id/home_indexing_action"
-                app:layout_constraintTop_toTopOf="parent"
-                app:layout_constraintVertical_chainStyle="packed"
-                tools:text="Status" />
+                android:animateLayoutChanges="true">
 
-            <com.google.android.material.progressindicator.LinearProgressIndicator
-                android:id="@+id/home_indexing_progress"
-                android:layout_width="match_parent"
-                android:layout_height="wrap_content"
-                android:indeterminate="true"
-                app:indeterminateAnimationType="disjoint"
-                app:layout_constraintBottom_toBottomOf="@+id/home_indexing_action"
-                app:layout_constraintTop_toTopOf="@+id/home_indexing_action"
-                app:trackColor="@color/sel_track" />
+                <TextView
+                    android:id="@+id/home_indexing_status"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:layout_margin="@dimen/spacing_medium"
+                    android:gravity="center"
+                    android:textAppearance="@style/TextAppearance.Auxio.BodyLarge"
+                    app:layout_constraintBottom_toTopOf="@+id/home_indexing_action"
+                    app:layout_constraintTop_toTopOf="parent"
+                    app:layout_constraintVertical_chainStyle="packed"
+                    tools:text="Status" />
 
-            <Button
-                android:id="@+id/home_indexing_action"
-                android:layout_width="match_parent"
-                android:layout_height="wrap_content"
-                android:text="@string/lbl_retry"
-                android:visibility="invisible"
-                app:layout_constraintBottom_toBottomOf="parent"
-                app:layout_constraintTop_toBottomOf="@+id/home_indexing_status" />
+                <com.google.android.material.progressindicator.LinearProgressIndicator
+                    android:id="@+id/home_indexing_progress"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:layout_marginStart="@dimen/spacing_medium"
+                    android:layout_marginEnd="@dimen/spacing_medium"
+                    android:indeterminate="true"
+                    app:indeterminateAnimationType="disjoint"
+                    app:layout_constraintBottom_toBottomOf="@+id/home_indexing_action"
+                    app:layout_constraintTop_toTopOf="@+id/home_indexing_action"
+                    app:trackColor="@color/sel_track" />
 
-        </androidx.constraintlayout.widget.ConstraintLayout>
+                <Button
+                    android:id="@+id/home_indexing_action"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:text="@string/lbl_retry"
+                    android:layout_marginStart="@dimen/spacing_medium"
+                    android:layout_marginEnd="@dimen/spacing_medium"
+                    android:layout_marginBottom="@dimen/spacing_medium"
+                    android:visibility="invisible"
+                    app:layout_constraintBottom_toBottomOf="parent"
+                    app:layout_constraintTop_toBottomOf="@+id/home_indexing_status" />
 
-        <androidx.viewpager2.widget.ViewPager2
-            android:id="@+id/home_pager"
-            android:layout_width="match_parent"
-            android:layout_height="match_parent"
-            app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
-            app:layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior"
-            tools:layout="@layout/fragment_home_list" />
+            </androidx.constraintlayout.widget.ConstraintLayout>
+
+        </com.google.android.material.card.MaterialCardView>
 
     </FrameLayout>