AsyncTask 和Timer同时使用

package com.example.test; 
 
import java.net.URL; 
import java.util.Timer; 
import java.util.TimerTask; 
 
import javax.xml.parsers.SAXParser; 
import javax.xml.parsers.SAXParserFactory; 
 
import org.xml.sax.InputSource; 
import org.xml.sax.XMLReader; 
 
import android.app.Activity; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.os.Handler; 
import android.util.Log; 
 
public class MyXmlPoller extends Activity { 
 
    private Handler handler = new Handler(); 
 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main); 
 
        new Timer().schedule(new MyTimerTask(), 0, 1000); 
    } 
 
    private class MyAsyncTask extends AsyncTask { 
 
        protected MyData doInBackground(Integer... counter) { 
            MyData myData = new MyData(); 
 
            try { 
                URL url = new URL("http://www.example.com/my.xml"); 
                SAXParserFactory spf = SAXParserFactory.newInstance(); 
                SAXParser sp = spf.newSAXParser(); 
 
                XMLReader xr = sp.getXMLReader(); 
 
                MySAXHandler mySAXHandler = new Handler(); 
                xr.setContentHandler(mySAXHandler); 
 
                xr.parse(new InputSource(url.openStream())); 
 
                myData = mySAXHandler.getParsedData(); 
 
                return myData; 
 
            } catch (Exception e) { 
                Log.e("!!!!!!!!!! MyAsyncTask doInBackground error", e.getMessage(), e); 
                return myData; 
            } 
 
        } 
 
        protected void onPostExecute(MyData myData) { 
            Log.d("+++++++++++++ MyAsyncTask onPostExecute", myData.toString()); 
        } 
    } // MyAsyncTask 
 
   private Handler mHandler = new Handler();  
 
public class MyTimerTask extends TimerTask { 
    public void run() { 
        mHandler.post( 
            new Runnable() {  
                public void run() {  
                    new MyAsyncTask().execute(""); 
                }  
            };      
        ) 
    } 
} } 

 在这里呢一定要注意TimerTask要运行在Handler中。

 

当然上面的代码也可以如下变化

URL url = new URL("http://www.example.com/my.xml"); 
            SAXParserFactory spf = SAXParserFactory.newInstance(); 
            SAXParser sp = spf.newSAXParser(); 
 
            XMLReader xr = sp.getXMLReader(); 
 
            MyHandler myHandler = new MyHandler(); 
            xr.setContentHandler(myHandler); 

 

将上面的放在onPreExecute() method 中。

http://developer.android.com/intl/fr/reference/android/os/Looper.html