My app needs to be in portrait mode so I set it in the manifest by:
android:screenOrientation=\"portrait\"
But I just recently added anothe
In your fragment FragA :
@Override
public void onResume() {
    super.onResume();
    getActivity().setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}
@Override
public void onPause() {
    getActivity().setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    super.onPause();
}
onPause method code ensure your activity back to portrait orientation
First Fragment:
@Override
    public void onResume() {
        super.onResume();
        getActivity().setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    }
Second Fragment:
     @Override
        public void onResume() {
            super.onResume();
 getActivity().setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED);
   }