There is a method to change it programmatically but that method is not exposed. There doesn't seem to be anything else to change it programmatically from what I have read.
However, I did come across this one stackoverflow answer that uses reflection to do it. Please upvote the answer there if it works for you: https://stackoverflow.com/a/19819843/3286163
The answer was for a listview but is the same for the scrollview:
ScrollView scr = (ScrollView)findViewById(R.id.scrollView1);
try
{
Field mScrollCacheField = View.class.getDeclaredField("mScrollCache");
mScrollCacheField.setAccessible(true);
Object mScrollCache = mScrollCacheField.get(scr); // scr is your Scroll View
Field scrollBarField = mScrollCache.getClass().getDeclaredField("scrollBar");
scrollBarField.setAccessible(true);
Object scrollBar = scrollBarField.get(mScrollCache);
Method method = scrollBar.getClass().getDeclaredMethod("setVerticalThumbDrawable", Drawable.class);
method.setAccessible(true);
// Set your drawable here.
method.invoke(scrollBar, getResources().getDrawable(R.drawable.scrollbar_blue));
}
catch(Exception e)
{
e.printStackTrace();
}
Only thing I could find. I gave it a try myself and it worked.