Listview没有显示使用asynctask

Question

我在XML Parsing中使用asynctask来加载listview asyncronously中的数据。当我使用Log.d()时，我发现xmlparsing正常工作并显示log中的所有数据。但是当我尝试从异步任务中加载到listview中时，listview没有显示任何内容。像数据这样的数据并不是在列表视图中加载。

我的XMLParsing类

  

XMLParser.java

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package com.askme.exploretoday;


import java.io.IOException;
import java.io.StringReader;
import java.io.UnsupportedEncodingException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import android.util.Log;

public class XMLParser {
	public String getXmlFromUrl(String url) {
        String xml = null;
 
        try {
            // defaultHttpClient+
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
 
            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            xml = EntityUtils.toString(httpEntity);
 
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        // return XML
        return xml;
    }
	
	
	public Document getDomElement(String xml){
        Document doc = null;
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        try {
 
            DocumentBuilder db = dbf.newDocumentBuilder();
 
            InputSource is = new InputSource();
                is.setCharacterStream(new StringReader(xml));
                doc = db.parse(is); 
 
            } catch (ParserConfigurationException e) {
                Log.e("Error: ", e.getMessage());
                return null;
            } catch (SAXException e) {
                Log.e("Error: ", e.getMessage());
                return null;
            } catch (IOException e) {
                Log.e("Error: ", e.getMessage());
                return null;
            }
                // return DOM
            return doc;
    }
	public String getValue(Element item, String str) {      
	    NodeList n = item.getElementsByTagName(str);        
	    return this.getElementValue(n.item(0));
	}
	 
	public final String getElementValue( Node elem ) {
	         Node child;
	         if( elem != null){
	             if (elem.hasChildNodes()){
	                 for( child = elem.getFirstChild(); child != null; child = child.getNextSibling() ){
	                     if( child.getNodeType() == Node.TEXT_NODE  ){
	                         return child.getNodeValue();
	                     }
	                 }
	             }
	         }
	         return "";
	  } 

}

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My List数据类，有助于将数据作为对象加载并传输适配器类中的所有数据

  

ListData.java

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package com.askme.exploretoday;

public class ListData {
	 
    String Description;
    String title;
    String details;
    public String getDetails() {
		return details;
	}

	public void setDetails(String details) {
		this.details = details;
	}

	public String getDescription() {
            return Description;
    }

    public void setDescription(String description) {
            Description = description;
    }

    public String getTitle() {
            return title;
    }

    public void setTitle(String title) {
            this.title = title;
    }

}

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这是listview

的类

  

list_activity.java   

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package com.askme.exploretoday;


import java.util.ArrayList;
import java.util.List;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;


import android.app.Activity;
import android.app.Application;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.AdapterView.OnItemClickListener;

public class list_activity extends Activity {
	ProgressDialog loading;
	MyBaseAdapter adapter0,adapter1;
		ListView lvDetail;
		TextView tv;
		String xmlLink;
		Context context = list_activity.this;
        ArrayList<ListData> myList0 = new ArrayList<ListData>();
        ArrayList<ListData>myList1= new ArrayList<ListData>();

        @Override
        protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.caption_list);

                xmlLink=getIntent().getExtras().getString("newspaper_name");
                lvDetail = (ListView) findViewById(R.id.lvCustomList);


        		tv=(TextView) findViewById(R.id.news_caption);

                try{
                new backgroundProcess().execute(adapter0,adapter1);
                }catch(Exception e){
                	tv.setText(e.toString());
                }





		        lvDetail.setOnItemClickListener(new OnItemClickListener() {

					@Override
					public void onItemClick(AdapterView<?> parent,
							View view, int position, long id) {
						// TODO Auto-generated method stub
						String url=adapter0.getItem(position).getDescription();
						String c=adapter0.getItem(position).getTitle();
						String d=adapter0.getItem(position).getDetails();
						Intent intent=new Intent(context,newsPaper_launcher.class);
						intent.putExtra("URL", url);
						intent.putExtra("Title",c);
						intent.putExtra("Description",d);
						startActivity(intent);
					}
				});




		        }


    	public class backgroundProcess extends AsyncTask<MyBaseAdapter, Integer, MyBaseAdapter>{

			@Override
			protected void onPreExecute() {
				// TODO Auto-generated method stub
				loading=new ProgressDialog(context);
		        loading.setProgressStyle(ProgressDialog.STYLE_SPINNER);
		        loading.setMessage("Please wait...");
		        loading.setIndeterminate(true);
		        loading.setCancelable(true);
		        loading.show();

			}
			@Override
			protected MyBaseAdapter doInBackground(MyBaseAdapter... adapterArray) {
				// TODO Auto-generated method stub

				// insert fake data into the list before setting the adapter
                // otherwise it will generate NullPointerException  - Obviously

                ListData ld = new ListData();
                ld.setTitle("fakeData");
                ld.setDescription("fakeData");
                ld.setDetails("fake Data");
                myList0.add(ld);
                myList1.add(ld);



                adapterArray[0]=new MyBaseAdapter(context, myList0);
				adapter0=new MyBaseAdapter(context, myList0);
        		String title,address,details;
            	XMLParser parser = new XMLParser();
            	String xml = null;
            	try{
            		xml=parser.getXmlFromUrl(xmlLink);
//            		xml=parser.getXmlFromUrl("http:/newagebd.net/feed/");
//            		xml=parser.getXmlFromUrl("http://www.ittefaq.com.bd/rss.xml");
//                xml= parser.getXmlFromUrl("http://bdnews24.com/?widgetName=rssfeed&widgetId=1150&getXmlFeed=true"); // getting XML
//            	xml=parser.getXmlFromUrl("http://thebangladeshtoday.com/feed/");
//            	xml=parser.getXmlFromUrl("http://bangla.bdnews24.com/?widgetName=rssfeed&widgetId=1151&getXmlFeed=true");
//            	xml=parser.getXmlFromUrl("http://www.amardeshonline.com/pages/rss");
            	}catch(Exception e)
            	{
            		tv.setText(e.toString());
            	}
				Element cap,url,news;
				ListData temp;
                Document doc = parser.getDomElement(xml); // getting DOM element
                NodeList caption=doc.getElementsByTagName("title");
                NodeList link = doc.getElementsByTagName("link");
                NodeList fullNews=doc.getElementsByTagName("description");
                	for (int i = 2; i < link.getLength(); i++) {
                    cap = (Element) caption.item(i);
                    url = (Element) link.item(i);
                    news=(Element) fullNews.item(i);
                   title = parser.getValue(cap, "title");
                   address = parser.getValue(url, "link");
                   details=parser.getValue(news, "description");
						Log.i("INFO Check",title+"\n"+address+"\n"+details);
						temp = new ListData();
                   temp.setTitle(title);
                   temp.setDescription(address);
                   temp.setDetails(details);
                   myList0.add(temp);
                }

                myList0.remove(0);

                adapter0.notifyDataSetChanged();
                adapterArray[0].notifyDataSetChanged();

				return adapterArray[0];

			}
                @Override
    			protected void onPostExecute(MyBaseAdapter result) {
    				// TODO Auto-generated method stub
                	loading.cancel();
    				lvDetail.setAdapter(adapter0);
//    				super.onPostExecute(result);
    			}

			}



}

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我的BaseAdapter类，用于加载listview中的数据

  

MyBaseAdapter.java

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package com.askme.exploretoday;

import java.util.ArrayList;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
 
public class MyBaseAdapter extends BaseAdapter {
        
        ArrayList<ListData> myList = new ArrayList<ListData>();
        LayoutInflater inflater;
        Context context;
        public MyBaseAdapter(Context context, ArrayList<ListData> myList) {
                this.myList = myList;
                this.context = context;
                inflater = LayoutInflater.from(this.context);        // only context can also be used
        }
 
        @Override
        public int getCount() {
                return myList.size();
        }
 
        @Override
        public ListData getItem(int position) {
                return myList.get(position);
        }
 
        @Override
        public long getItemId(int position) {
                return 0;
        }
 
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
                MyViewHolder mViewHolder;
                
                if(convertView == null) {
                        convertView = inflater.inflate(R.layout.list_item, null);
                        mViewHolder = new MyViewHolder();
                        convertView.setTag(mViewHolder);
                } else {
                        mViewHolder = (MyViewHolder) convertView.getTag();
                }
                
                
                mViewHolder.tvTitle = detail(convertView, R.id.tvTitle, myList.get(position).getTitle());
                	if(mViewHolder.tvTitle.toString().isEmpty())
                		mViewHolder.tvTitle.setText("ERROR");
                return convertView;
        }
        
        // or you can try better way
        private TextView detail(View v, int resId, String text) {
                TextView tv = (TextView) v.findViewById(resId);
                tv.setText(text);
                return tv;
        }
        
        
        private class MyViewHolder {
                TextView tvTitle;
        }
 
}

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