packages/SystemUI/res/anim/heads_up_exit.xml

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
        >
    <translate
            android:interpolator="@android:interpolator/overshoot"
            android:fromYDelta="0" android:toYDelta="-50%"
            android:duration="@android:integer/config_shortAnimTime" />
    <alpha
        android:interpolator="@android:interpolator/accelerate_quad"
        android:fromAlpha="1.0" android:toAlpha="0.0"
        android:duration="@android:integer/config_shortAnimTime" />
</set>