Fragment add show hide 方法无效 求大神帮忙看一下哪里的问题？

Adapter.setOnItemClickLitener(new GalleryAdapter.OnItemClickLitener() {
@Override
public void onItemClick(View view, int position) {

            FragmentManager fragmentManager = getActivity().getFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            switch (position) {
                case 0:
                      fragmentTransaction.hide(allsinFragment);
                        fragmentTransaction.add(R.id.id_fragment_content, sinFragment);

                        fragmentTransaction.addToBackStack(null);

                    break;
            }
            fragmentTransaction.commit();
        }
    });

上面是我的代码 求指点哪里出了问题呢，一直是重叠的，而且我的fragment是动态添加。。

add完之后要show啊，你调用了hide方法，隐藏掉了，然后没有在前台显示的fragment