使用Android自带DownloadManager下载文件

SDK在API Level 9中加入了DownloadManager服务，可以将长时间的下载任务交给系统，完全由系统管理。

 

package com.hebaijun.downloadtest;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;

import android.app.Activity;
import android.app.DownloadManager;
import android.app.DownloadManager.Request;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
import android.webkit.MimeTypeMap;

public class DownloadTestActivity extends Activity {
 private DownloadManager downloadManager;
 private SharedPreferences prefs;
 private static final String DL_ID = "downloadId";
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        downloadManager = (DownloadManager)getSystemService(DOWNLOAD_SERVICE);
        prefs = PreferenceManager.getDefaultSharedPreferences(this);
    }
 @Override
 protected void onPause() {
  // TODO Auto-generated method stub
  super.onPause();
  unregisterReceiver(receiver);
 }
 @Override
 protected void onResume() {
  // TODO Auto-generated method stub
  super.onResume();
  if(!prefs.contains(DL_ID)) {
   String url = "http://10.0.2.2/android/film/G3.mp4";
         //开始下载
         Uri resource = Uri.parse(encodeGB(url));
         DownloadManager.Request request = new DownloadManager.Request(resource);
         request.setAllowedNetworkTypes(Request.NETWORK_MOBILE | Request.NETWORK_WIFI);
         request.setAllowedOverRoaming(false);
         //设置文件类型
         MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
         String mimeString = mimeTypeMap.getMimeTypeFromExtension(MimeTypeMap.getFileExtensionFromUrl(url));
         request.setMimeType(mimeString);
         //在通知栏中显示
         request.setShowRunningNotification(true);
         request.setVisibleInDownloadsUi(true);
         //sdcard的目录下的download文件夹
         request.setDestinationInExternalPublicDir("/download/", "G3.mp4");
         request.setTitle("移动G3广告");
         long id = downloadManager.enqueue(request);
         //保存id
         prefs.edit().putLong(DL_ID, id).commit();
     } else {
         //下载已经开始，检查状态
         queryDownloadStatus();
     }

     registerReceiver(receiver, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
 }
 
 /**
  * 如果服务器不支持中文路径的情况下需要转换url的编码。
  * @param string
  * @return
  */
 public String encodeGB(String string)
 {
  //转换中文编码
  String split[] = string.split("/");
  for (int i = 1; i < split.length; i++) {
   try {
    split[i] = URLEncoder.encode(split[i], "GB2312");
   } catch (UnsupportedEncodingException e) {
    e.printStackTrace();
   }
   split[0] = split[0]+"/"+split[i];
  }
  split[0] = split[0].replaceAll("\\+", "%20");//处理空格
  return split[0];
 }
 
 private BroadcastReceiver receiver = new BroadcastReceiver() {
     @Override
     public void onReceive(Context context, Intent intent) {
      //这里可以取得下载的id，这样就可以知道哪个文件下载完成了。适用与多个下载任务的监听
      Log.v("intent", ""+intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, 0));
         queryDownloadStatus();
     }
 };
 
 private void queryDownloadStatus() {
     DownloadManager.Query query = new DownloadManager.Query();
     query.setFilterById(prefs.getLong(DL_ID, 0));
     Cursor c = downloadManager.query(query);
     if(c.moveToFirst()) {
         int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
         switch(status) {
         case DownloadManager.STATUS_PAUSED:
          Log.v("down", "STATUS_PAUSED");
         case DownloadManager.STATUS_PENDING:
          Log.v("down", "STATUS_PENDING");
         case DownloadManager.STATUS_RUNNING:
             //正在下载，不做任何事情
          Log.v("down", "STATUS_RUNNING");
             break;
         case DownloadManager.STATUS_SUCCESSFUL:
             //完成
             Log.v("down", "下载完成");
             break;
         case DownloadManager.STATUS_FAILED:
             //清除已下载的内容，重新下载
          Log.v("down", "STATUS_FAILED");
          downloadManager.remove(prefs.getLong(DL_ID, 0));
             prefs.edit().clear().commit();
             break;
         }
     }
 }
}