Use corner radius attr instead of fixed value

<inset xmlns:android="http://schemas.android.com/apk/res/android">

    <shape android:shape="rectangle">

        <corners android:radius="2dp" />

        <corners android:radius="?android:attr/dialogCornerRadius" />

        <solid android:color="?android:attr/colorBackground" />

    </shape>

</inset>