pulse_out_repeat.xml

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <scale
        android:fromXScale="0.1"
        android:fromYScale="0.1"
        android:toXScale="1"
        android:toYScale="1"
        android:pivotX="50%"
        android:pivotY="50%"
        android:duration="1500"
        android:repeatCount="infinite"
        />

    <alpha
        android:fromAlpha="1"
        android:toAlpha="0.1"
        android:duration="1500"
        android:repeatCount="infinite"
     />
</set>