Question

I’d like to know if my Activity was displayed because the user pressed back
on some other Activity. In the Lifecycle I couldn’t identify any Callbacks
that are robustly giving me that info.

onRestart() is not working. It will also fire if the Apps Task was brought to front.
onResume() will not work for the same reason.

I suppose there is a simple solution for that, but in Android supposedly simple things can be pretty nasty.

Answer 1

Call your 2nd activity with startActivityForResult(Intent, int), then override the onBackPressed() in the 2nd activity and have it setResult() to RESULT_CANCELED. Lastly, have the 1st activity catch that in onActivityResult().

Code example:

Activity 1:

Intent i = new Intent(Activity1.this, Activity2.class);
startActivityForResult(i, 0);

---

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == 0) {
        if (resultCode == RESULT_CANCELED) {
                // user pressed back from 2nd activity to go to 1st activity. code here
        }
    }
}

Activity 2:

@Override
public void onBackPressed() {
    setResult(RESULT_CANCELED);
    finish();
}