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

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
    </style>

    <style name="dialog_margin">
        <item name="android:layout_marginTop">16dp</item>
        <item name="android:layout_marginLeft">4dp</item>
        <item name="android:layout_marginRight">4dp</item>
        <item name="android:layout_marginBottom">4dp</item>
    </style>

</resources>