Android - Eclipse Graphic Layout how to see selector

I have a simple button selector:

    <?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://ift.tt/nIICcg">
<item android:drawable="@drawable/button_pressed" android:state_pressed="true"/>


</selector>

I applied it to a button already and it works fine on the device. I want to preview the selector but how do i give a button focus or a pressed state in the xml graphical layout tab so the selector can be triggered ? My end goal is to see the selector in the graphical layout so i can more quickly alter it.