detail: show name when scrolling

Show the name of the currently shown detail item when scrolling. This
is just UI candy that I've always wanted to add but couldn't due to
CollapsingToolbarLayout being a mess. This addition circumvents that
by simply doing some reflection magic and hooking the alpha of the
toolbar title to the current scroll state, solving the issue.

app/src/main/java/org/oxycblt/auxio/detail/AlbumDetailFragment.kt

@@ -64,7 +64,7 @@ class AlbumDetailFragment : DetailFragment() {
 
         binding.lifecycleOwner = viewLifecycleOwner
 
-        setupToolbar(R.menu.menu_album_detail) { itemId ->
+        setupToolbar(detailModel.curAlbum.value!!, R.menu.menu_album_detail) { itemId ->
             if (itemId == R.id.action_queue_add) {
                 playbackModel.addToUserQueue(detailModel.curAlbum.value!!)
                 requireContext().showToast(R.string.lbl_queue_added)

app/src/main/java/org/oxycblt/auxio/detail/ArtistDetailFragment.kt

@@ -73,7 +73,7 @@ class ArtistDetailFragment : DetailFragment() {
 
         binding.lifecycleOwner = viewLifecycleOwner
 
-        setupToolbar()
+        setupToolbar(detailModel.curArtist.value!!)
         setupRecycler(detailAdapter) { pos ->
             // If the item is an ActionHeader we need to also make the item full-width
             val item = detailAdapter.currentList[pos]

app/src/main/java/org/oxycblt/auxio/detail/DetailAppBarLayout.kt

@@ -0,0 +1,133 @@
+package org.oxycblt.auxio.detail
+
+import android.animation.ValueAnimator
+import android.content.Context
+import android.util.AttributeSet
+import android.view.View
+import android.view.ViewGroup
+import androidx.annotation.StyleRes
+import androidx.appcompat.widget.AppCompatTextView
+import androidx.appcompat.widget.Toolbar
+import androidx.coordinatorlayout.widget.CoordinatorLayout
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.appbar.AppBarLayout
+import org.oxycblt.auxio.R
+import org.oxycblt.auxio.ui.EdgeAppBarLayout
+
+/**
+ * An [EdgeAppBarLayout] variant that also shows the name of the toolbar whenever the detail
+ * recyclerview is scrolled beyond it's first item (a.k.a the header). This is used instead of
+ * CollapsingToolbarLayout since that thing is a mess with crippling bugs and state issues.
+ * This just works.
+ */
+class DetailAppBarLayout @JvmOverloads constructor(
+    context: Context,
+    attrs: AttributeSet? = null,
+    @StyleRes defStyleAttr: Int = -1
+) : EdgeAppBarLayout(context, attrs, defStyleAttr) {
+    private var mTitleView: AppCompatTextView? = null
+    private var mRecycler: RecyclerView? = null
+
+    private var titleShown: Boolean? = null
+    private var mTitleAnimator: ValueAnimator? = null
+
+    override fun onAttachedToWindow() {
+        super.onAttachedToWindow()
+
+        (layoutParams as CoordinatorLayout.LayoutParams).behavior = Behavior(context)
+    }
+
+    private fun findTitleView(): AppCompatTextView {
+        val titleView = mTitleView
+
+        if (titleView != null) {
+            return titleView
+        }
+
+        val toolbar = findViewById<Toolbar>(R.id.detail_toolbar)
+
+        val newTitleView = Toolbar::class.java.getDeclaredField("mTitleTextView").run {
+            isAccessible = true
+            get(toolbar) as AppCompatTextView
+        }
+
+        newTitleView.alpha = 0f
+
+        mTitleView = newTitleView
+        return newTitleView
+    }
+
+    private fun findRecyclerView(): RecyclerView {
+        val recycler = mRecycler
+
+        if (recycler != null) {
+            return recycler
+        }
+
+        val newRecycler = (parent as ViewGroup).findViewById<RecyclerView>(R.id.detail_recycler)
+
+        mRecycler = newRecycler
+        return newRecycler
+    }
+
+    private fun setTitleVisibility(visible: Boolean) {
+        if (titleShown == visible) return
+
+        titleShown = visible
+
+        if (mTitleAnimator != null) {
+            mTitleAnimator!!.cancel()
+            mTitleAnimator = null
+        }
+
+        val titleView = findTitleView()
+        val from: Float
+        val to: Float
+
+        if (visible) {
+            from = 0f
+            to = 1f
+        } else {
+            from = 1f
+            to = 0f
+        }
+
+        if (titleView.alpha == to) return
+
+        mTitleAnimator = ValueAnimator.ofFloat(from, to).apply {
+            addUpdateListener {
+                titleView.alpha = it.animatedValue as Float
+            }
+
+            duration = resources.getInteger(R.integer.app_bar_elevation_anim_duration).toLong()
+
+            start()
+        }
+    }
+
+    class Behavior @JvmOverloads constructor(
+        context: Context? = null,
+        attrs: AttributeSet? = null
+    ) : AppBarLayout.Behavior(context, attrs) {
+        override fun onNestedPreScroll(
+            coordinatorLayout: CoordinatorLayout,
+            child: AppBarLayout,
+            target: View,
+            dx: Int,
+            dy: Int,
+            consumed: IntArray,
+            type: Int
+        ) {
+            super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type)
+
+            val appBar = child as DetailAppBarLayout
+            val recycler = appBar.findRecyclerView()
+
+            val showTitle = (recycler.layoutManager as LinearLayoutManager)
+                .findFirstVisibleItemPosition() > 0
+
+            appBar.setTitleVisibility(showTitle)
+        }
+    }
+}

app/src/main/java/org/oxycblt/auxio/detail/DetailFragment.kt

@@ -31,6 +31,7 @@ import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentDetailBinding
+import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.ui.SortMode
 import org.oxycblt.auxio.ui.memberBinding
@@ -70,14 +71,18 @@ abstract class DetailFragment : Fragment() {
 
     /**
      * Shortcut method for doing setup of the detail toolbar.
+     * @param music Music data to use as the toolbar title
      * @param menu Menu resource to use
      * @param onMenuClick (Optional) a click listener for that menu
      */
     protected fun setupToolbar(
+        data: Music,
         @MenuRes menu: Int = -1,
         onMenuClick: ((itemId: Int) -> Boolean)? = null
     ) {
         binding.detailToolbar.apply {
+            title = data.name
+
             if (menu != -1) {
                 inflateMenu(menu)
             }

app/src/main/java/org/oxycblt/auxio/detail/GenreDetailFragment.kt

@@ -64,7 +64,7 @@ class GenreDetailFragment : DetailFragment() {
 
         binding.lifecycleOwner = viewLifecycleOwner
 
-        setupToolbar()
+        setupToolbar(detailModel.curGenre.value!!)
         setupRecycler(detailAdapter) { pos ->
             val item = detailAdapter.currentList[pos]
             item is Header || item is ActionHeader || item is Genre

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

@@ -47,6 +47,7 @@ import kotlin.math.sqrt
  * - Use modified Auxio resources instead of AFS resources
  * - Variable names are no longer prefixed with m
  * - Made path management compat-friendly
+ * - Converted to kotlin
  */
 class FastScrollPopupDrawable(context: Context) : Drawable() {
     private val paint: Paint = Paint().apply {

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

@@ -38,6 +38,7 @@ import org.oxycblt.auxio.util.systemBarsCompat
  * this class was primarily written by me.
  *
  * TODO: Add a swipe-up behavior a la Phonograph. I think that would improve UX.
+ *  - We need to use a separate drag helper to prevent issues
  * TODO: Leverage this layout to make more tablet-friendly UIs
  *
  * @author OxygenCobalt

app/src/main/java/org/oxycblt/auxio/ui/EdgeAppBarLayout.kt

@@ -38,7 +38,7 @@ import org.oxycblt.auxio.util.systemBarsCompat
  * **Note:** This layout relies on [AppBarLayout.liftOnScrollTargetViewId] to figure out what
  *  scrolling view to use. Failure to specify this will result in the layout not working.
  */
-class EdgeAppBarLayout @JvmOverloads constructor(
+open class EdgeAppBarLayout @JvmOverloads constructor(
     context: Context,
     attrs: AttributeSet? = null,
     @StyleRes defStyleAttr: Int = -1

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

@@ -13,7 +13,7 @@
             android:layout_width="match_parent"
             android:layout_height="match_parent">
 
-            <org.oxycblt.auxio.ui.EdgeAppBarLayout
+            <org.oxycblt.auxio.detail.DetailAppBarLayout
                 android:id="@+id/detail_appbar"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
@@ -25,7 +25,7 @@
                     android:id="@+id/detail_toolbar"
                     style="@style/Widget.Auxio.Toolbar.Icon" />
 
-            </org.oxycblt.auxio.ui.EdgeAppBarLayout>
+            </org.oxycblt.auxio.detail.DetailAppBarLayout>
 
             <org.oxycblt.auxio.ui.EdgeRecyclerView
                 android:id="@+id/detail_recycler"