android - clearing background when replacing listfragments in the same area -

i have typical setup on left there listfragment displaying categories while on right listfragement displays details.

for example:

when category selected:

left  right     a1 b     a2 c 

when category b selected:

  left  right         b1     b          c 

now when switching between , b on left right side updates correctly showing 2 lines a1,a2 , 1 line b1. (clearing a2)

now give option @ different data of , b a1 (lower a) has a1 (not a1 , a2, a1, a2)

i replacing right listfragment 1 displaying caps a1,a2, b2... second listfragment displaying lower a1, b2...

the problem when replacing right listfragmentcaps listfragmentlower right area not cleared , on sees on screen:

left  right (with listfragmentcaps)     a1 b     a2 c 

switching listfragmentlower

left  right (with listfragmentlower)     a1 b     a2  <- left on of listfragmentcaps c 

the **a2** listfragmentcaps still visible though listfragmentlower has replaced it. other screen content of listfragmentcaps still visible (like checkboxes) while listfragmentlower not have checkboxes.

what best way clear area before listfragmentlower shows content?

ps hope long text description clear :-) many thanks

if use static fragments, have replace them dynamic ones. see post