Can I gain some efficiency by declaring appropriate members "static" in Android Activity

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

One thing please DO NOT use singleTask or singleInstance for this purpose. The activity launch flags are there to control how activity stacks behave. They have visible impact on the user interaction with your activity (making it non-standard). Those modes are intended to be used when you want that kind of user interaction, they should NOT be used to change the implementation details of your app.

Answer 2

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.