<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
    <item
       android:state_pressed="true"
       android:drawable="@drawable/drink_inject_button_selected"/>
    <item
        android:drawable="@drawable/drink_inject_button_regular"/>

</selector>

Add selector for the drink inject button
Add selector for the drink inject button
