Question

I wish to know is it possible to write an android app that when it runs at the background, it can track user activities?(Such as what other app did the user used, what phone number did user dial, the GPS location for user, etc) Cause I am not sure can a single android app react to other application, does anyone know the answer? Thanks

Answer 1

In the general case, no, you can’t. And users would probably prefer it so.

Once this has been said, there are certain partial solutions. Sometimes the system is so helpful that it will publish Intents reflecting user actions: for example when the user uninstalls an app — with the caveat that you don’t get that intent on the app itself being uninstalled.

It used to be the case that before Jelly Bean (4.1) apps could read the log that other applications publish and try to extract info from there, but it was a cumbersome, error prone, ungrateful task. For example, the browser shows nothing when it navigates to a certain page. You may read the logs for a while with adb logcat to get a feeling of what was possible and what isn’t. This action requires the relevant permission, which cannot be held by regular apps now.

Thanks to @WebnetMobile for the heads up about logs and to @CommonsWare for the link, see the comments below.