If it derives from Application, add the fully qualified (namespace + class name) as the android:name
parameter of the application element in your manifest.
<application
android:name="com.you.yourapp.ApplicationEx"
Or if the class’ package can be described as relative to the package
in the manifest
tag, then just start with a .
:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.you.yourapp">
<application
android:name=".ApplicationEx"