Android refresh fragment listview at onrestart of fragmentactivity

Question

From my FragmentActivity, i want to update my ListView of a Fragment(created by code) at onRestart of the FragmentActivity. There is no fragment and tag in XML file. Here is my FragmentActivity.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    viewPager = (ViewPager) findViewById(R.id.pager);
    mAdapter = new ProfilePagerAdapter(getSupportFragmentManager(),
                    myFriendsList, notifiedFriendsList);
    viewPager.setAdapter(mAdapter);
    ..........

my FragmentPagerAdapter is

public class ProfilePagerAdapter extends FragmentPagerAdapter {

private ArrayList<Friend> myFriends;
private ArrayList<ExpandableChild> notifiedFriendsList;
private SparseArray<Fragment> registeredFragments = new SparseArray<Fragment>();

public ProfilePagerAdapter(FragmentManager fm, ArrayList<Friend> myFriends, ArrayList<ExpandableChild> notifiedFriendsList) {
    super(fm);
    // TODO Auto-generated constructor stub
    this.myFriends = myFriends;
    this.notifiedFriendsList = notifiedFriendsList;
}

@Override
public Fragment getItem(int index) {

    switch (index) {
    case 0:
        return new FriendsFragment(myFriends);
    case 1:
        return new MyProfileFragment(notifiedFriendsList);
    }

    return null;
}

@Override
public int getCount() {
    return 2;
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
    Fragment fragment = (Fragment) super.instantiateItem(container, position);
    registeredFragments.put(position, fragment);
    return fragment;
}

@Override
public void destroyItem(ViewGroup container, int position, Object object) {
    registeredFragments.remove(position);
    super.destroyItem(container, position, object);
}

public Fragment getRegisteredFragment(int position) {
    return registeredFragments.get(position);
}

In my FriendsFragment class, i have a ListView. I used following two methods to update the ListView from my FragmentActivity in the class.

public void setNewFriendList(ArrayList<Friend> myFriends){
    this.friendsList = myFriends;
}

public void updateList(){
    adapter.notifyDataSetChanged();
}

Now i want to update the ListView of FriendsFragment at onRestart() of FragmentActivity in following way.

@Override
protected void onRestart() {
    // TODO Auto-generated method stub
    super.onRestart();
    android.support.v4.app.Fragment frag = mAdapter
            .getRegisteredFragment(0);
    if (frag != null) {
        ((FriendsFragment) frag).setNewFriendList(myFriendsList);
        ((FriendsFragment) frag).updateList();
        Toast.makeText(UserProfileTab.this, "Updated",Toast.LENGTH_LONG).show();
    } else {
      Toast.makeText(UserProfileTab.this, "Not Updated:",Toast.LENGTH_LONG).show();
    }
}

But in Toast shows Not Updated as frag returns null. I followed link1 and link1. Thanks in advance.