android: Handle checked state in activated background

src/frontends/android/app/src/main/res/drawable/activated_background.xml

@@ -23,6 +23,10 @@
         android:state_activated="true"
         android:drawable="@color/accent" />
 
+    <item
+        android:state_checked="true"
+        android:drawable="@color/checked" />
+
     <item
         android:drawable="@android:color/transparent" />
 

src/frontends/android/app/src/main/res/values/colors.xml

@@ -39,6 +39,9 @@
     <color
         name="panel_separator">#5a5a5a</color>
 
+    <color
+        name="checked">#4a4a4a</color>
+
     <color
         name="pressed">#5a5a5a</color>