How to make transparent gradient?

I have the following gradient:

<?xml version="1.0" encoding="utf-8"?>
    <shape xmlns:android="http://schemas.android.com/apk/res/android">
        <gradient 
            android:startColor="#ECECEC"
            android:centerColor="#F6F6F4"
            android:endColor="#F8F8F6"
            android:angle="90"
            android:dither="true"
         />
    </shape>

I want this to be transparent because in my ListView I am setting this as my ListSelector:

<ListView android:layout_width="fill_parent"
                android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android"
                android:id="@+id/ARListView" 
                android:background="@drawable/transparent_background" 
                android:cacheColorHint="#00000000" android:drawSelectorOnTop="true" 
                android:listSelector="@drawable/stocks_selected_gradient">
</ListView>

Answer

Just use an 8-digit color value, e.g. #FFF8F8F6, where the first two characters are the alpha value. FF being fully opaque, and 00 being fully transparent.