How does android:noHistory="true" work?

Question

Lets say I have a base activity with a menu, when I click on menu item A, it goes to activity A. I open the menu again, and go to B. From B I go back to A, and back and fourth like this for a while.

So the stack would be A, B, A, B, A, B, .... And when I hit the back button, it goes backwards through the stack as expected.

However lets say I don't want this functionality, so I add to my manifest, android:noHistory="true". So when I hit the back button it exits the application instead of going though the stack.

Now the illusion makes it seem, lets say if I'm in activity A, I use the menu and go to activity B, the stack would just be B, because I can't go back to A.

But, when using noHistory="true", does the true stack of A, B, A, B, A, B exist? Rather, is every call to an activity by using the menu instantiating a new copy of that activity, but the user can't see it? Would this be causing resource issues?

Or when noHistory="false", does the back button just call something like startAcitvity(intent) again or is it going through each new copy that was instantiated?

I'm concerned with resource issues and not slowing down a users android device.

Answer 1

From the docs about noHistory:

A value of "true" means that the activity will not leave a historical trace. It will not remain in the activity stack for the task, so the user will not be able to return to it.

Regarding your question:

does the true stack of A, B, A, B, A, B exist?

The docs would indicate no.

I'm concerned with resource issues and not slowing down a users android device.

You really don't need to worry about this. The OS should handle the cleanup of activities when memory is getting low. Its more likely that poor use of bitmaps or logic in your activities will result in performance slowdowns.