Background for dialog on Android 4.x appcompat

I'm developing an apk and I want the dialogues to have an appearance like this

is now ready but in Android 4.x it is not shown that way. It looks like this

    <style name="AppTheme_AlertDialog" parent="Theme.AppCompat.Light.Dialog.Alert">
            <item name="android:windowBackground">@drawable/dialogo_back</item>
            <item name="android:topDark">@drawable/dialogo_title</item>
            <item name="android:gravity">center</item>
            <item name="android:divider">#0000</item>
            <item name="android:dividerHeight">2dp</item>
            <item name="android:layout_gravity">center</item>
            <item name="android:colorAccent">@color/colorPrimaryDark</item>
            <item name="android:windowTitleStyle">@style/Titulo</item>
    </style>

Could someone tell me how to do it appcompat? : D