<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:fillAfter="false" >

    <scale
        android:duration="100"
        android:fromXScale="1"
        android:fromYScale="1"
        android:pivotX="50%"
        android:pivotY="50%"
        android:toXScale="2"
        android:toYScale="2" >
    </scale>

</set>