问如何动态地从当前的android应用程序下载现有的apk文件？

EN

package com.helloandroid.imagedownloader;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import org.apache.http.util.ByteArrayBuffer;
import android.util.Log;

   public class ImageManager {
   private final String PATH = "/data/data/com.helloandroid.imagedownloader/";  //put the downloaded file here
   public void DownloadFromUrl(String imageURL, String fileName) {  //this is the downloader method

   try {

         URL url = new URL("http://yoursite.com/" + imageURL); //you can write here any link

            File file = new File(fileName);



             long startTime = System.currentTimeMillis();

             Log.d("ImageManager", "download begining");

             Log.d("ImageManager", "download url:" + url);

            Log.d("ImageManager", "downloaded file name:" + fileName);

            /* Open a connection to that URL. */

             URLConnection ucon = url.openConnection();



             /*

              * Define InputStreams to read from the URLConnection.

             */

            InputStream is = ucon.getInputStream();

             BufferedInputStream bis = new BufferedInputStream(is);



             /*

              * Read bytes to the Buffer until there is nothing more to read(-1).

              */

             ByteArrayBuffer baf = new ByteArrayBuffer(50);

             int current = 0;

             while ((current = bis.read()) != -1) {

                     baf.append((byte) current);

             }



             /* Convert the Bytes read to a String. */

            FileOutputStream fos = new FileOutputStream(file);

            fos.write(baf.toByteArray());

             fos.close();

            Log.d("ImageManager", "download ready in"

                             + ((System.currentTimeMillis() - startTime) / 1000)

                             + " sec");



    } catch (IOException e) {

            Log.d("ImageManager", "Error: " + e);

     }



    }

 }