Android 断点续传

import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.HttpURLConnection;
 import java.net.URL;import com.lenovo.lsf.push.messagecenter.db.FileDownload;
 import com.lenovo.lsf.push.messagecenter.db.FileDownloadDAO;
 import com.lenovo.lsf.push.messagecenter.db.IFileDownloadDAO;import android.content.Context;
 import android.content.Intent;
 import android.os.Environment;
 import android.util.Log;
 import android.widget.Toast;public class DownLoader {
  public int progress = 0;
  public int flag = 0;// 判断是第几次点击 下载 按钮
 // public static int remainFileSize = 0;
  static Context context; private IFileDownloadDAO fileDAO;
 public DownLoader(Context context) {
   DownLoader.context = context;
   fileDAO = new FileDownloadDAO(context); }
 public HttpURLConnection conn = null;
 public void startDownload(String urlString,String FBID,int theUpdateProgressBarNumber) {
   if (Environment.getExternalStorageState().equals(
     Environment.MEDIA_MOUNTED)) {
        
   FileDownload fileDownload = new FileDownload();
   fileDownload.setFBID(FBID);  if (null != conn)
    conn.disconnect();  File savePath = new File(Environment.getExternalStorageDirectory()
     .toString() + "/lenovo"); // String saveName = urlString.substring(urlString.lastIndexOf("/") + 1);
   String saveName = FBID;  
   
   fileDownload.setFileName(saveName);  savePath.mkdirs();
  File saveTo = new File(savePath, saveName);
   if (!saveTo.exists())
    try {
     saveTo.createNewFile();
    } catch (IOException e2) {
     // TODO Auto-generated catch block
     e2.printStackTrace();
    }
   InputStream is = null;
   BufferedOutputStream fos = null;  int status = -1;
  long downloadedFileSize = 0;
  if (saveTo != null)
    downloadedFileSize = saveTo.length();  try {
    URL url = new URL(urlString);   conn = (HttpURLConnection) url.openConnection();
    conn.setConnectTimeout(30 * 1000);
    conn.setReadTimeout(30 * 1000);
    conn.setRequestProperty("Range", "bytes=" + downloadedFileSize
      + "-");   status = conn.getResponseCode();
    if (status == HttpURLConnection.HTTP_OK
      || status == HttpURLConnection.HTTP_PARTIAL) {    if (flag == 0) {
     // remainFileSize = conn.getContentLength();
      fileDownload.setFileSize(conn.getContentLength());
     }    if (!fileDAO.queryAllFBID().contains(
       fileDownload.getFBID()))
      fileDAO.addFile(fileDownload);    is = conn.getInputStream();
    fos = new BufferedOutputStream(new FileOutputStream(saveTo,
       true));    int lenth = -1;
     byte[] buffer = new byte[1024];
     while ((lenth = is.read(buffer)) != -1) {
      progress = (int) (downloadedFileSize * 100.0 / fileDAO
        .selectFileSizeByFileName(saveName));
      downloadedFileSize = downloadedFileSize + lenth;     if (downloadedFileSize <= fileDAO
        .selectFileSizeByFileName(saveName))
       fos.write(buffer, 0, lenth);     Intent intent = new Intent("update_progressbar"+theUpdateProgressBarNumber);
      intent.putExtra("progress", progress);
      context.sendBroadcast(intent);     if (downloadedFileSize == fileDAO
        .selectFileSizeByFileName(saveName)) {
       Intent intent2 = new Intent("update_button");
       context.sendBroadcast(intent2);
      }    }
    } else {
    }
   } catch (Exception e) {
    e.printStackTrace();
   } finally {
    if (fos != null) {
     try {
      fos.flush();
     } catch (IOException e1) {
      e1.printStackTrace();
     }
     try {
      fos.close();
     } catch (IOException e) {
      e.printStackTrace();
     }
    }
    if (is != null) {
     try {
      is.close();
     } catch (IOException e) {
      e.printStackTrace();
     }
    }
    if (conn != null) {
     conn.disconnect();
    }  }
   }
   else
   {
    Toast.makeText(context, "SD卡不可用", Toast.LENGTH_LONG);
    
   }
  }}