zumo_2.0_android/app/src/main/res/drawable/rectangle_dim_top.xml

<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle" >

  <gradient
    android:angle="90"
    android:endColor="#4D000000"
    android:startColor="#00000000"
    android:type="linear" />

  <corners
    android:radius="0dp"/>
</shape>