在Android应用程序布局上，我如何定位视图，使其始终显示在中间下方一半的距离？

I'm using a Relative layout as the root or parent container and I have two buttons to place inside this Layout. The buttons need to be placed one on top of the other. The problem is that I want to position these buttons so that they appear below the center of the view but not directly below. That is within the bottom half of the view I want the buttons to appear halfway along that half portion. I tried adding a the buttons as children of a RelativeLayout (that was centered in the middle) inside the parent RelativeLayout and that sort of achieves what I'm trying to but then the Eclipse complains with a warning stating that one set of Relative Layout tags is useless and that I should consider getting rid of it.I'm using a Relative layout as the root or pare