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。

直接看实例代码：

 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;
             }
         }
     }
 }

最后需要的权限是：

<uses-permission android:name="android.permission.INTERNET"/>

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

如果需要隐藏下载工具的提示和显示，修改代码：

request.setShowRunningNotification(false);

request.setVisibleInDownloadsUi(false);

加入下面的权限：

<uses-permission android:name="android.permission.DOWNLOAD_WITHOUT_NOTIFICATION"/>

http://blog.csdn.net/lixiang0522/article/details/7608310