You don't need star_half.
Try to do like this:
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="@android:id/background" android:drawable="@drawable/star_none" />
<item android:id="@android:id/secondaryProgress" android:drawable="@drawable/star_none" />
<item android:id="@android:id/progress" android:drawable="@drawable/star_fill" />
</layer-list>