heart_beat.xml

<set
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android:interpolator/accelerate_decelerate"
    android:ordering="sequentially"
    android:repeatCount="infinite">

    <scale
        android:startOffset="1200"
        android:duration="100"
        android:pivotX="50%"
        android:pivotY="50%"
        android:fromXScale="1.0"
        android:fromYScale="1.0"
        android:toXScale="0.8"
        android:toYScale="0.8" />

    <scale
        android:duration="100"
        android:pivotX="50%"
        android:pivotY="50%"
        android:fromXScale="0.8"
        android:fromYScale="0.8"
        android:toXScale="1.0"
        android:toYScale="1.0" />

</set>