Checking on what activity the customer is at

Hello everyone, I want to check if the customer is in a particular activity on his phone (e.g .: and then he will be shown a screen in my app. (To be displayed on the screen of the application he opened whose activity is …)

I would be happy for help on how to do it.

this most probably will not work anymore in newer Android versions…

you will have to write an extension for that

It does not help me … in Kodular I can not insert codes, and I also do not know how to develop extensions …

Maybe you can build me an extension that does this or bring me a link to a neat guide on how to build extensions.