Animation Slide Fragment

I am working on an application that displays a fragment. As soon as the user clicks the button on the fragment, this fragment will be reduced by 80%, showing another fragment below. The problem I am facing is that when I press the button, the fragment goes down 80%, but after the screen is simply drawn only with the second fragment displayed. Any help?

I have provided a code that runs when a button is clicked. and animation files

 public void onClick(View v) {
    // TODO Auto-generated method stub

    switch(v.getId())
    {
        case R.id.button1:

            ProfileFragment pro = new ProfileFragment();


    ((MainActivity) getActivity()).tra =((MainActivity)     ()).fragmentManager.beginTransaction();                         

             ((MainActivity) getActivity()).mFragmentStack.add(pro.toString());
   getActivity()).tra.setCustomAnimations(R.anim.slide_in_top, R.anim.slide_out_bottom);
             ((MainActivity) getActivity()).tra.replace(R.id.fragment_swap,pro);

             ((MainActivity) getActivity()).tra.addToBackStack(pro.toString());
             ((MainActivity) getActivity()).tra.commit();

            break;

    }

}

Slide_out_bottom:

     <?xml version="1.0" encoding="utf-8"?>
         <set xmlns:android="http://schemas.android.com/apk/res/android" >

            <translate
               android:duration="900"
               android:fromYDelta="0%"
               android:toYDelta="80%"
            />


      </set>

slide_in_top:

   <?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android" >

<translate
    android:duration="900"
    android:fromYDelta="0%"
    android:toYDelta="0%" />
</set>