Is there a good way to hide the border which is between buttons of list when focused a button?

How-to
1

What LVGL version are you using?

v8.1

What do you want to achieve?

There is always a border between two buttons of list, it is good. But when I focused a button, the top border of the above button is always there.
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So how to hide it ?

What have you tried so far?

I try lv_obj_set_style_border_width(button, 0, LV_STATE_FOCUS_KEY);
But I find that the border is belong to the above one not focused button;
So what should i do?