res/drawable/launcher_screen.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
  <item android:drawable="@android:color/white"/>

  <item
      android:drawable="@drawable/app_icon"
      android:height="150dp"
      android:width="150dp"
      android:gravity="center"/>

</layer-list>