Updated libraries.

app/src/main/res/drawable/traditional_slider_thumb.xml

@@ -1,8 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<shape xmlns:android="http://schemas.android.com/apk/res/android"
-    android:shape="oval">
-    <size
-        android:width="16dp"
-        android:height="16dp" />
-    <solid android:color="@android:color/black" />
-</shape>

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

@@ -10,13 +10,12 @@
         android:layout_height="wrap_content"
         android:layout_gravity="center"
         android:padding="30dp"
-        seekarc:clockwise="false"
-        seekarc:max="120"
-        seekarc:progressColor="?colorAccent"
-        seekarc:rotation="180"
-        seekarc:startAngle="30"
-        seekarc:sweepAngle="300"
-        seekarc:thumb="@drawable/traditional_slider_thumb" />
+        seekarc:SeekArc_clockwise="false"
+        seekarc:SeekArc_max="120"
+        seekarc:SeekArc_progressColor="?colorAccent"
+        seekarc:SeekArc_rotation="180"
+        seekarc:SeekArc_startAngle="30"
+        seekarc:SeekArc_sweepAngle="300" />
 
     <TextView
         android:id="@+id/timer_display"

app/src/main/res/values/styles.xml

@@ -28,7 +28,6 @@
 
     <style name="TraditionalMusicProgressSlider" parent="TraditionalMusicProgressSliderParent">
         <item name="android:thumbOffset">0dp</item>
-        <item name="android:thumb">@drawable/traditional_slider_thumb</item>
     </style>
 
     <style name="Toolbar">