Possible to 'layer' Android applications?

Question

I know this in general is beyond the scope of SO, but I am looking for some basic yes/no info to see if it is even feasible to proceed... I am thinking about building and Android 'note-taking/annotation' app that runs 'over' other installed Android apps, such as the web browser for example.

Essentially, while the user is browsing, my app would be running in the bg as a service, and then they could activate it which would then essentially intercept user inputs and translate those on a transparent canvas over the web browser into lines, shapes, etc. The user could then take a screen-cap of their marking with the underlying web page, which would be stored to the sd card.

Answer 1

This is a very good idea and a great question, but sadly, I do not believe it is possible.

The way Android is designed only one Activity can have focus at a time, while a Service could run in the background, the user would not be able to interact with it. The user can only interact with the currently active Activity.

Again, love the idea, but it is sadly not supported.