Should I resume a scroll view to last viewed location or last intended location?

Question

As with many apps, I have a scroll view for data. This data can be scrolled normally, and as with almost all scroll views like this, it has the ability for inertia scrolling — to keep scrolling once a finger has been released from the screen depending on the prior velocity.

If someone begins an inertia scroll, then taps on a button outside of this scrolling view that replaces the viewport, should I…

• Continue the scrolling in the background?
  The scroll would therefore stop at the point where the scroll would have ceased if the user not pressed the button.

• Stop the scroll at the point that was last visible before the button was pressed?

• Return the scroll view to the top when the user returns?

^{This is intended for an iOS app if it makes any difference.
I've seen this question, but the situation there is regarding a change in data. My data has remained the same.}

Answer 1

Superb question, and a tough one. I had to think this one over during my daily Zombie Run! However - this is what I feel is the right thing to do.

The scrolling even if you don't have your finger there is present for a reason. The reason is to stop the scrolling when you reach the chunk of information you're interested in, nothing else. This leads me to the conclusion that the continual scrolling would be graphical interesting but of no use. It would be like having a carusel you can't stop (!) and wouldn't give the user any benefit in functionality.

Thus, the scrolling should stop imediately when the button is pushed, and when the user returns, the state should be where she left it. Nothing else makes sense (if you're not into unuseful moving objects). Your second option has my vote.