scrollbar moves rough when activating fastscrollenable in android listview

Question

scrollbar moves roughly while scrolling. how to make scrollbar move smoothly when enable fastcrollenable="true"?

I've been looking for it for a month. both in android documentation, stackoverflow, and other web ,but i can't find it.

in my listview , im just add....

android:fastScrollEnabled="true"

Answer 1

setSmoothScrollbarEnabled(boolean enabled)
When smooth scrollbar is enabled, the position and size of the scrollbar thumb is 
computed based on the number of visible pixels in the visible items.

note that sometimes your answer would be easily found in java