Add light animation when scrolling listings.

app/src/main/java/com/github/apognu/otter/fragments/AlbumsFragment.kt

@@ -1,14 +1,10 @@
 package com.github.apognu.otter.fragments
 
 import android.content.Context
-import android.graphics.Bitmap
 import android.os.Bundle
-import android.util.DisplayMetrics
-import android.view.Gravity
 import android.view.View
 import android.view.animation.AccelerateDecelerateInterpolator
 import androidx.appcompat.app.AppCompatActivity
-import androidx.core.graphics.drawable.toDrawable
 import androidx.core.os.bundleOf
 import androidx.fragment.app.Fragment
 import androidx.recyclerview.widget.RecyclerView
@@ -25,7 +21,6 @@ import com.github.apognu.otter.views.LoadingFlotingActionButton
 import com.squareup.picasso.Picasso
 import jp.wasabeef.picasso.transformations.RoundedCornersTransformation
 import kotlinx.android.synthetic.main.fragment_albums.*
-import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Dispatchers.IO
 import kotlinx.coroutines.Dispatchers.Main
 import kotlinx.coroutines.GlobalScope
@@ -139,6 +134,24 @@ class AlbumsFragment : FunkwhaleFragment<Album, AlbumsAdapter>() {
     }
   }
 
+  override fun onResume() {
+    super.onResume()
+
+    var coverHeight: Float? = null
+
+    scroller.setOnScrollChangeListener { _: View?, _: Int, scrollY: Int, _: Int, _: Int ->
+      if (coverHeight == null) {
+        coverHeight = cover.measuredHeight.toFloat()
+      }
+
+      cover.translationY = (scrollY / 2).toFloat()
+
+      coverHeight?.let { height ->
+        cover.alpha = (height - scrollY.toFloat()) / height
+      }
+    }
+  }
+
   inner class OnAlbumClickListener : AlbumsAdapter.OnAlbumClickListener {
     override fun onClick(view: View?, album: Album) {
       openTracks(context, album, fragment = this@AlbumsFragment)

app/src/main/java/com/github/apognu/otter/fragments/PlaylistTracksFragment.kt

@@ -80,6 +80,20 @@ class PlaylistTracksFragment : FunkwhaleFragment<PlaylistTrack, PlaylistTracksAd
       }
     }
 
+    var coverHeight: Float? = null
+
+    scroller.setOnScrollChangeListener { _: View?, _: Int, scrollY: Int, _: Int, _: Int ->
+      if (coverHeight == null) {
+        coverHeight = covers.measuredHeight.toFloat()
+      }
+
+      covers.translationY = (scrollY / 2).toFloat()
+
+      coverHeight?.let { height ->
+        covers.alpha = (height - scrollY.toFloat()) / height
+      }
+    }
+
     play.setOnClickListener {
       CommandBus.send(Command.ReplaceQueue(adapter.data.map { it.track }.shuffled()))
 

app/src/main/java/com/github/apognu/otter/fragments/TracksFragment.kt

@@ -92,6 +92,20 @@ class TracksFragment : FunkwhaleFragment<Track, TracksAdapter>() {
       refreshDownloadedTracks()
     }
 
+    var coverHeight: Float? = null
+
+    scroller.setOnScrollChangeListener { _: View?, _: Int, scrollY: Int, _: Int, _: Int ->
+      if (coverHeight == null) {
+        coverHeight = cover.measuredHeight.toFloat()
+      }
+
+      cover.translationY = (scrollY / 2).toFloat()
+
+      coverHeight?.let { height ->
+        cover.alpha = (height - scrollY.toFloat()) / height
+      }
+    }
+
     play.setOnClickListener {
       CommandBus.send(Command.ReplaceQueue(adapter.data.shuffled()))