The Stream from Google Classroom is split into different elements so, depending on the type of elements you have and want to retrieve from the Classroom Stream, you might benefit from checking the following requests:
Retrieving the announcements
GET https://classroom.googleapis.com/v1/courses/{courseId}/announcements
Retrieving the courseworks
GET https://classroom.googleapis.com/v1/courses/{courseId}/courseWork
Retrieving the coursework materials
GET https://classroom.googleapis.com/v1/courses/{courseId}/courseWorkMaterials
Note
Also, please bear in mind that all these requests will return the information needed only if the user making the request has access and the necessary permissions for retrieving it.
The quickstart you mentioned is a Java one - so in order to make it work for Android you will have to adapt it properly to your needs.
Reference
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