在范围内无法访问 News 类型的封闭实例

Question

我正在尝试添加到 RSS Feed 阅读器 (ListActivity) ActionBar - (http://www.edumobile.org/android/android-tutorial/rssreader-in-android-development/)
我已经使用 Fragment 来做到这一点。

现在我遇到了错误，我不知道如何解决它

No enclosing instance of the type News is accessible in scope

错误在：

rssadaptor = new RSSListAdaptor(News.this, R.layout.newslist,itemlist);
                                //Here

progress = ProgressDialog.show(
                                News.this, null, "Loading RSS Feeds...");
                                //Here

LayoutInflater vi = (LayoutInflater)News.this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                                   //Here

以下是活动的完整代码：

package com.rss.test.actionbar;

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.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.text.Html;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class News extends ActionBarActivity {
    private static ArrayList<NewsItem> itemlist = null;
    private static MyFragment.RSSListAdaptor rssadaptor = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ActionBar actionbar = getSupportActionBar();
    setContentView(R.layout.news);

    actionbar.setDisplayShowCustomEnabled(true);

    itemlist = new ArrayList<NewsItem>();

    MyFragment fragment = new MyFragment();
    getSupportFragmentManager().beginTransaction().replace(android.R.id.content, fragment).commit();

   fragment.new RetrieveRSSFeeds().execute();
}

public static class MyFragment extends ListFragment {
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getActivity();
    }

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

            NewsItem data = itemlist.get(position);

            Intent intent = new Intent(Intent.ACTION_VIEW,Uri.parse(data.link));

            startActivity(intent);

          }

    private void retrieveRSSFeed(String urlToRssFeed,ArrayList<NewsItem> 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("/*RSS Url*/",itemlist);

                    rssadaptor = new RSSListAdaptor(News.this, R.layout.newslist,itemlist);

                    return null;
            }

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

            @Override
            protected void onPreExecute() {
                    progress = ProgressDialog.show(
                            News.this, null, "Loading RSS Feeds...");

                    super.onPreExecute();
            }

            @Override
            protected void onPostExecute(Void result) {
                ListView l = (ListView)getActivity().findViewById(R.id.list);
                l.setAdapter(rssadaptor);

                    progress.dismiss();

                    super.onPostExecute(result);
            }

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

    private class RSSListAdaptor extends ArrayAdapter<NewsItem>{
        private List<NewsItem> objects = null;

                public RSSListAdaptor(Context context, int textviewid, List<NewsItem> objects) {
                        super(context, 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 NewsItem 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)News.this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                                view = vi.inflate(R.layout.newslist, null);
                        }

                        NewsItem data = objects.get(position);

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

                                title.setText(data.title);
                                date.setText("on " + data.date);

                                description.setText(Html.fromHtml(data.description));
                        }

                        return view;
                }
        }   


}





}

Answer 1

像您的片段这样的static 内部类无法访问外部类实例OuterClass.this。

对于片段中的Context，使用getActivity() 而不是OuterClass.this。

Answer 2

因为MyFragment 是静态类，所以您可以在RetrieveRSSFeeds 中访问News Activity 上下文。

只需使用RetrieveRSSFeeds 类构造函数即可在doInBackground 中获取Activity 上下文：

public Context mContext;
public RetrieveRSSFeeds(Context mContext){
  this.mContext=mContext;
}

来自活动：

 fragment.new RetrieveRSSFeeds(News.this).execute();