我开发了一个基于碎片的应用程序。
我有一个带按钮的菜单片段，这些按钮每打开一个新的片段，替换上一个。
问题是，一些片段需要一段时间才能打开，因为它会调用一些asynctasks并填充一些listview。
因此，当我按下菜单片段中的按钮时，它会保持冻结2秒，直到新的片段取代菜单片段出现。
我希望在该时间出现一个微调器或“加载..”对话框。
我已经测试过了

private progressDialog progressDialog;
        progressDialog = new ProgressDialog(this);
        progressDialog.setIndeterminate(true);
        progressDialog.setMessage("Loading...");
        progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        progressDialog.show();

这段代码显示了对话框，但当屏幕冻结时它从不显示。
我应该把代码放在哪里？在包含所有片段的Activity中，还是在菜单片段中？或者可能在加载的片段中？
我不能完成这个任务，所以当我在菜单片段中按下按钮时，我会执行以下代码。

NewAppointmentFragment fragment = new NewAppointmentFragment();
                android.support.v4.app.FragmentTransaction fragmentTransaction =

        getActivity().getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.fragment_container, fragment, 
        "NewAppointmentFragment");
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();

但它需要2秒，直到这个新的片段被加载并出现冻结的2秒，你可以看到按下按钮的菜单片段

可能是因为我在新片段中调用了所有asynctasks和操作来填充OnCreateView中的列表视图？

如何解决此问题？
先谢了
我的菜单片段

@Override
         public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
         View rootView = inflater.inflate(R.layout.fragment_main, container, false);

         nextAppointmentsButton = (Button) 
         rootView.findViewById(R.id.nextAppointmentsButton);
         nuevaCitaButton = (Button) rootView.findViewById(R.id.nuevaCitaButton);
         nearbyPharmaciesButton = (Button) 
         rootView.findViewById(R.id.nearbyPharmaciesButton);
         ourLocationButton = (Button) rootView.findViewById(R.id.ourLocationButton);

         nextAppointmentsButton.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
                UpcomingAppointmentsFragment fragment = new 
         UpcomingAppointmentsFragment();
                android.support.v4.app.FragmentTransaction fragmentTransaction =

          getActivity().getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.fragment_container, fragment);
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();

            }

         });

         nuevaCitaButton.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
                 ((MainActivity)getActivity()).showProgressDialog();
                 NewAppointmentFragment fragment = new NewAppointmentFragment();
                 android.support.v4.app.FragmentTransaction fragmentTransaction =

         getActivity().getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.fragment_container, fragment, 
         "NewAppointmentFragment");
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();
            }

        });

        nearbyPharmaciesButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                NearbyPharmaciesFragment fragment = new NearbyPharmaciesFragment();
                android.support.v4.app.FragmentTransaction fragmentTransaction =

        getActivity().getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.fragment_container, fragment);
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();

            }

        });
        ourLocationButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                OurLocationMapFragment fragment = new OurLocationMapFragment();
                android.support.v4.app.FragmentTransaction fragmentTransaction =

        getActivity().getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.fragment_container, fragment);
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();
            }

        });

        // Inflate the layout for this fragment
        return rootView;
        }

当我按下菜单按钮时加载了我的新片段

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {
       View rootView = inflater.inflate(R.layout.fragment_new_appointment, 
        container, false);

      // **Calls to asynctasks **
      // **Populate operations ListViews**

      return rootView;
      }