res/anim/slideshow_out.xml

<?xml version="1.0" encoding="utf-8"?>
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android:interpolator/accelerate_quad" 
    android:fromAlpha="1.0"
    android:toAlpha="0.0"
    android:duration="1500"
/>