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它适用于 wifi 或 3g，但在断开连接时强制关闭。我正在从教程中学习，所以不确定，但我相信代码中考虑了互联网断开连接。

完成 logcat http://pastebin.com/aAEGwfFk

代码：

package org.tatvamoksh.tml;

import java.util.ArrayList;
import java.util.HashMap;

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

import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;


public class Updates extends ListActivity {

    public ArrayList<HashMap<String, String>> mylist;
    public ListAdapter adapter;
    public ProgressDialog progressDialog; 

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.updates_item);


        mylist = new ArrayList<HashMap<String, String>>();

        adapter = new SimpleAdapter(this, mylist , R.layout.updates, 
                        new String[] { "event", "notice" }, 
                        new int[] { R.id.event_title, R.id.notice });


        final ListView lv = getListView();
        lv.setTextFilterEnabled(true);  
/*        lv.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {              
                @SuppressWarnings("unchecked")
                HashMap<String, String> o = (HashMap<String, String>) lv.getItemAtPosition(position);                   
                Toast.makeText(Updates.this, "ID '" + o.get("id") + "' was clicked.", Toast.LENGTH_LONG).show(); 

            }
        });
*/        
        progressDialog = ProgressDialog.show(Updates.this, "Getting updates", "Please wait...");
        new GetDataTask().execute();        

    }

    private Boolean isOnline()  {
        ConnectivityManager cm = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo ni = cm.getActiveNetworkInfo();
        if(ni != null && ni.isConnected())
            return true;

        return false;
    }

    private class GetDataTask extends AsyncTask<Void, Void, Integer> {

        @Override
        protected Integer doInBackground(Void... params) {



            // Simulates some delay
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e1) {
                e1.printStackTrace();
            }

            if(isOnline()){
                mylist.clear();                  

                String xml = XMLfunctions.getXML();
                Document doc = XMLfunctions.XMLfromString(xml);

                int numResults = XMLfunctions.numResults(doc);

                if((numResults <= 0)){
                    Toast.makeText(Updates.this, "Geen resultaten gevonden", Toast.LENGTH_LONG).show();  
                    finish();
                }

                NodeList nodes = doc.getElementsByTagName("update");

                for (int i = 0; i < nodes.getLength(); i++) {                           
                    HashMap<String, String> map = new HashMap<String, String>();    

                    Element e = (Element)nodes.item(i);
                    map.put("id", XMLfunctions.getValue(e, "id"));
                    map.put("event", "Event:" + XMLfunctions.getValue(e, "event"));
                    map.put("notice", "Update: " + XMLfunctions.getValue(e, "notice"));
                    mylist.add(map);            
                }
            }
            else{
                Toast.makeText(Updates.this, "No connection..", Toast.LENGTH_LONG).show();          
            }

            return 1;
        }

        @Override
        protected void onPostExecute(Integer result) {

            setListAdapter(adapter);
            progressDialog.dismiss();
            super.onPostExecute(result);
        }
    }
}

我确实尝试搜索类似的问题，大多数导致 NullPointerException，调试器没有捕获任何（我认为） 调试器透视图

4

1 回答 1

0

消除

Toast.makeText(Updates.this, "No connection..", Toast.LENGTH_LONG).show();

现在在那个空的 else 中，让你的 AsyncTask 返回另一个值（例如 2）

else{
   return 2;
}

如果你在return 1;里面移动if(isOnline()，那么你可以摆脱 else 并简单地写return 2;，但这只是可读性的问题。

然后在 中onPostExecute()，检查值是否为 2，然后制作 Toast。

    @Override
    protected void onPostExecute(Integer result) {
    if (result == 1){
        setListAdapter(adapter);
        progressDialog.dismiss();
        super.onPostExecute(result);
    }
    else
      Toast.makeText(Updates.this, "No connection..", Toast.LENGTH_LONG).show();          
    }
于 2013-02-05T04:31:36.000 回答