Android + Google Analytics how to track correctly?

Question

Android

The whole evening I argued with the programmer how to set up Google Analytics in the Android application.
There is an application. It has n categories with pictures.
Required: Statistics on how many pictures the user has viewed per session. + all other analytics data by sessions/new/average number of views
The programmer suggests:
When scrolling through category images, create a counter and send the counter+category for analytics at the end.
It also offers app/section launches and image views as separate events. That is, on the main analytics, it will write how many categories the user opened per session and not how many pictures he viewed ..
I suggest:
When starting, send main+1
When opening a picture, send img+1 + category n
.....
Who is right?