Update activity_main.xml

Update the apps background color for material you.

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

@@ -3,7 +3,8 @@
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:orientation="vertical">
+    android:orientation="vertical"
+     android:background="?attr/colorSurface">
 
     <androidx.coordinatorlayout.widget.CoordinatorLayout
         android:id="@+id/drawer_layout"