Question

If an Activity is a singleton in practice, I think I can gain some efficiency by declaring appropriate members “static”, with zero risk. Yes?

Answer 1

The Android documentation says –

there’s never more than one instance
of a “singleTask” or “singleInstance”
activity, so that instance is expected
to handle all new intents.

This means you can use static members.

Besides, a standard or singleTop should have thread-safe static members only. Suppose the current activity stack is A-B-C-D. If the arriving intent is for an activity of type B which is in “standard” or “singleTop” mode. A new instance of B would be launched as (since B is not at the top of the stack), so the resulting stack would be A-B-C-D-B.