android - ListFragment 中的列表未更新

Question

我尝试在 ListFragment 中实现一个永无止境的列表（它基于为活动实现的现有代码）。

我有一个带有下一个代码的 ListFragment：

public class MainFragment extends ListFragment {

    //how many to load on reaching the bottom
    int itemsPerPage = 15;
    boolean loadingMore = false;


    ArrayList<String> myListItems;
    ArrayAdapter<String> adapter;

    ListView listview;
    //For test data :-)
    Calendar d = Calendar.getInstance();


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.e("Test", "Create Stories Fragment");
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

    }

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

        listview = (ListView) view.findViewById(android.R.id.list);
      //This will hold the new items
        myListItems = new ArrayList<String>();
        adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, myListItems);




        //add the footer before adding the adapter, else the footer will nod load!
        View footerView = ((LayoutInflater)getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listfooter, null, false);
        listview.addFooterView(footerView);

        //Set the adapter
        listview.setAdapter(adapter);


        //Here is where the magic happens
        listview.setOnScrollListener(new OnScrollListener(){

            //useless here, skip!
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {}

            //dumdumdum         
            @Override
            public void onScroll(AbsListView view, int firstVisibleItem,
                int visibleItemCount, int totalItemCount) {


                //what is the bottom iten that is visible
                int lastInScreen = firstVisibleItem + visibleItemCount;             

                //is the bottom item visible & not loading more already ? Load more !
                if((lastInScreen == totalItemCount) && !(loadingMore)){                 
                    Thread thread =  new Thread(null, loadMoreListItems);
                    thread.start();
                }
            }
        });


        //Load the first 15 items
        Log.e("Test", "Load first items");
        Thread thread =  new Thread(null, loadMoreListItems);
        thread.start();

        return view;
    }

    //Runnable to load the items 
    private Runnable loadMoreListItems = new Runnable() {           
        @Override
        public void run() {
            //Set flag so we cant load new items 2 at the same time
            loadingMore = true;

            //Reset the array that holds the new items
            myListItems = new ArrayList<String>();

            Log.e("Test", "simulate delay");
            //Simulate a delay, delete this on a production environment!
            try { Thread.sleep(1000);
            } catch (InterruptedException e) {}

            //Get 15 new listitems
            for (int i = 0; i < itemsPerPage; i++) {        

                //Fill the item with some bogus information
                myListItems.add("Date: " + (d.get(Calendar.MONTH)+ 1) + "/" + d.get(Calendar.DATE) + "/" + d.get(Calendar.YEAR) );              

                Log.e("Test", "Date: " + (d.get(Calendar.MONTH)+ 1) + "/" + d.get(Calendar.DATE) + "/" + d.get(Calendar.YEAR));
            // +1 day :-D
                d.add(Calendar.DATE, 1);

            }

            //Done! now continue on the UI thread
            getActivity().runOnUiThread(returnRes);

        }
    };  


    //Since we cant update our UI from a thread this Runnable takes care of that! 
    private Runnable returnRes = new Runnable() {
        @Override
        public void run() {

            Log.e("Test", "returnRes");
            //Loop thru the new items and add them to the adapter
            if(myListItems != null && myListItems.size() > 0){
                for(int i=0;i<myListItems.size();i++)
                {
                    Log.e("Test", "adding " + myListItems.get(i));
                    adapter.add(myListItems.get(i));
                }
            }

            Log.e("Test", "notifyDataSetChanged");

            //Tell to the adapter that changes have been made, this will cause the list to refresh
            adapter.notifyDataSetChanged();

            //Done loading more.
            loadingMore = false;
        }
    };

}

现在，listplaceholder.xml 很简单，与我从中获取的代码相同：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">    

    <ListView
        android:id="@id/android:list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:fastScrollEnabled="true"
        android:drawSelectorOnTop="false" />

    <TextView
        android:id="@id/android:empty"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:gravity="center"
        android:text="Loading data.."/>

</LinearLayout>

问题是，在原始代码中，我可以在向下滚动时看到更新的日期，在我的代码中，我只看到页脚消息 "Loading Data.." 。为什么列表没有更新？