How to force the selected row in the grid to scroll to the center

[Leowill]

I want to make the row in the center of gird. I try code like this:

myGridView.ensureVisible(rowIndex, 0, true);

or

myGridView.focusRow(rowIndex);

It just makes the row visible, sometimes the row is on the bottom of the grid.
Is there any method to make the row in the center of the gird.
I know that ,we should call scroller.setScrollTop() function, but I don't know the value to set.