Just add layout_weight="1" to in your linearLayout which having Buttons.
Edit :- let me make it simple
follow something like below, tags name may not be correct, it is just an Idea
<LL>// Top Parrent LinearLayout
<LL1 height="fill_parent" weight="1" "other tags as requirement"> <TV /><Butons /></LL1> // this layout will fill your screen.
<LL2 height="wrap_content" weight="1" orientation="Horizontal" "other tags as requirement"> <BT1 /><BT2/ ></LL2> // this layout gonna take lower part of button height of your screen
<LL/> TOP PARENT CLOSED