How to keep underling Activity visible until enter animation completes

Say I have Activity A and activity B. B has 'slide' set as the enter animation. 
I would like to slide B on top of A where A will remain untouched until animation completes and B is completely visible. 
Is that possible at all? In reality, when I try to do it Activity A disappears which leaves a blank screen and on top of that blank screen Activity B slides in  
