在ListFragment中刷新自定义ArrayList

Question

我正在尝试使用ListFragments和ViewPager制作RSS阅读器，这是我第一次使用ListFragment和ViewPager。我有六个选项卡，每个选项卡都有一个ListFragment。我已经为每个列表加载了一个类别的提要。我已经使用AsyncTask来做到这一点。第一次一切正常。但当我在标签上来回滑动时，一切都搞砸了。我得到每个页面上的列表，但列表项大小为0.所以我得到IndexOutOfBoundsException。我一直在寻找解决方案近4天了。但没发现运气。我认为onResume（）函数有一些错误。但我不确定那是什么。我把代码放在一个ListFragment中。我哪里出错了？

package com.example.feed;

import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;

import android.annotation.SuppressLint;
import android.app.ActionBar;
import android.support.v4.app.ListFragment;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;;

@SuppressLint("NewApi")
public class LatestNews extends ListFragment {

    private ArrayList<RSSItem> itemlist = null;
    private RSSLatestAdaptor rssadaptor = null;
    Bundle savedBundle = null;

    public static LatestNews newInstance(String text) {
        LatestNews pageFragment = new LatestNews();
        Bundle bundle = new Bundle();
        bundle.putString("test", text);
        pageFragment.setArguments(bundle);

        return pageFragment;
    }


    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        // return inflater.inflate(R.layout.sun_fragment, container, false);
        savedBundle = savedInstanceState;
        LinearLayout fragview = (LinearLayout) inflater.inflate(R.layout.main,
                container, false);

        itemlist = new ArrayList<RSSItem>();
        Log.e("Alert", "Latest News called");
        initList();

//      Log.d("List", ""+RefreshState.latestAdapter);
        ActionBar actionBar = getActivity().getActionBar();
        actionBar.show();
//      actionBar.setTitle("Latest");

        return fragview;
    }

    private void initList() {
        // TODO Auto-generated method stub
        int refreshState = RefreshState.latestNews;
        if(refreshState == 0)
            new RetrieveRSSFeeds().execute();
        else {
            rssadaptor = new RSSLatestAdaptor(getActivity(),
                    R.layout.rssitemview, RefreshState.latestAdapter);
            Log.d("Saved List", ""+rssadaptor.toString());
            Log.d("List Count", ""+rssadaptor.getCount());
            setListAdapter(rssadaptor);
            rssadaptor.notifyDataSetChanged();
        }

    }

    public void onResume() {
        super.onResume();
        rssadaptor.notifyDataSetChanged();
//      super.onResume();
    }

    private void retrieveRSSFeed(String urlToRssFeed, ArrayList<RSSItem> list) {
        try {
            URL url = new URL(urlToRssFeed);
            SAXParserFactory factory = SAXParserFactory.newInstance();
            SAXParser parser = factory.newSAXParser();
            XMLReader xmlreader = parser.getXMLReader();
            RSSParser theRssHandler = new RSSParser(list);

            xmlreader.setContentHandler(theRssHandler);

            InputSource is = new InputSource(url.openStream());

            xmlreader.parse(is);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private class RetrieveRSSFeeds extends AsyncTask<Void, Void, Void> {
        private ProgressDialog progress = null;

        @Override
        protected Void doInBackground(Void... params) {
            retrieveRSSFeed("http://www.example.com/feed", itemlist);
            RefreshState.latestAdapter = itemlist;
            rssadaptor = new RSSLatestAdaptor(getActivity(),
                    R.layout.rssitemview, itemlist);

            return null;
        }

        @Override
        protected void onCancelled() {
            super.onCancelled();
        }

        @Override
        protected void onPreExecute() {
            progress = ProgressDialog.show(getActivity(), null,
                    "Loading List...");

            super.onPreExecute();
        }

        @Override
        protected void onPostExecute(Void result) {
            setListAdapter(rssadaptor);

            progress.dismiss();
            RefreshState.latestNews = 1;
            super.onPostExecute(result);
        }

        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
        }
    }

    public class RSSLatestAdaptor extends ArrayAdapter<RSSItem> {
        private List<RSSItem> objects = null;

        public RSSLatestAdaptor(Context latestNews, int textviewid,
                ArrayList<RSSItem> objects) {
            super(latestNews, textviewid, objects);

            this.objects = objects;
        }

        @Override
        public int getCount() {
            return ((null != objects) ? objects.size() : 0);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public RSSItem getItem(int position) {
            return ((null != objects) ? objects.get(position) : null);
        }

        public View getView(int position, View convertView, ViewGroup parent) {
            View view = convertView;

            if (null == view) {
                LayoutInflater vi = (LayoutInflater) getActivity()
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                view = vi.inflate(R.layout.rssitemview, null);
            }

            RSSItem data = objects.get(position);

            if (null != data) {
                TextView title = (TextView) view.findViewById(R.id.txtTitle);
                TextView date = (TextView) view.findViewById(R.id.txtDate);
                TextView author = (TextView) view.findViewById(R.id.txtAuthor);

                title.setText(data.title);
                String dateCut = data.date.substring(0, 16);
                date.setText("on " + dateCut);
                author.setText("by " + data.creator);
            }

            return view;
        }
    }

    public void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);

        RSSItem data = itemlist.get(position);
        RSSItem data1 = itemlist.get(position + 1);
        // Intent intent = new
        // Intent(Intent.ACTION_VIEW,Uri.parse(data.author));
        // startActivity(intent);
        Log.d("Description", data.description);
        Intent detailRss = new Intent(getActivity(), RSSItemDetail.class);
        detailRss.putExtra("title", data.title);
        detailRss.putExtra("date", data.date);
        detailRss.putExtra("creator", data.creator);
        detailRss.putExtra("description", data1.description);
        detailRss.putExtra("link", data.link);

        // Log.d("Link to post", data.link);

        startActivity(detailRss);
    }

    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getActivity().getMenuInflater().inflate(R.menu.refresh_button, menu);
        getActivity().getMenuInflater().inflate(R.menu.rss_home, menu);

        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {

        case R.id.action_go_web:
            String url = "http://www.example.com";
            Intent browserIntent = new Intent(Intent.ACTION_VIEW);
            browserIntent.setData(Uri.parse(url));
            startActivity(browserIntent);
            break;

        case R.id.action_about:
            Intent aboutIntent = new Intent(getActivity(), About.class);
            startActivity(aboutIntent);
            break;

        case R.id.action_refresh:
            // Intent refreshIntent = new Intent(RssReaderActivity.this,
            // RssReaderActivity.class);
            // startActivity(refreshIntent);
            new RetrieveRSSFeeds().execute();
            break;

        default:
            break;
        }
        return true;
    }

}