Android DownloadManager的用法

DownloadManager是Android為開發人員提供的一個後台應用組件，它通過Http層進行檔案的下載任務.

一、直接操作Content Provider中的Downloads表實現！

    1：使用
         首先要在AndroidManifest.xml中申請訪問DownloadManager的許可權
          <permission android:name="android.permission.ACCESS_DOWNLOAD_MANAGER"/>
         添加一個下載任務：
         ContentValues values = new ContentValues();
         values.put(Downloads.URI, url);//指定
        values.put(Downloads.COOKIE_DATA, cookie);//如果下載Server需要cookie,設定cookie
        values.put(Downloads.VISIBILITY,Downloads.VISIBILITY_HIDDEN);//設定下載提示是否在螢幕頂部顯示
        values.put(Downloads.NOTIFICATION_PACKAGE, getPackageName());//設定下載完成之後回調的包名
        values.put(Downloads.NOTIFICATION_CLASS, DownloadCompleteReceiver.class.getName());//設定下載完成之後負責接收的Receiver，這個類要繼承BroadcastReceiver     
        values.put(Downloads.DESTINATION,save_path);//設定下載到的路徑，這個需要在Receiver裡自行處理
        values.put(Downloads.TITLE,title);//設定下載任務的名稱
        this.getContentResolver().insert(Downloads.CONTENT_URI, values);//將其插入到DownloadManager的資料庫中，資料庫會觸發修改事件，啟動下載任務

   2：如何為DownloadManager設定代理，比如Wap
             values.put(Downloads.PROXY_HOST,"10.0.0.172");
            values.put(Downloads.PROXY_PORT,"80");

  3:如何在下載過程中監聽下載任務
     可以通過監聽資料庫來實現
    DownloadsChangeObserver mDownloadObserver=new DownloadsChangeObserver(Downloads.CONTENT_URI);
    private class DownloadsChangeObserver extends ContentObserver {
        public DownloadsChangeObserver(Uri uri) {
            super(new Handler());
        }
        @Override
        public void onChange(boolean selfChange) {
            //查詢需要監聽的欄位
           //比如要監聽即時下載進度，查看當前下載狀態：是否已經斷開，或者下載失敗等等
           StringBuilder wherequery = new StringBuilder(Downloads.TITLE);
            wherequery.append("=");
            wherequery.append("'");
            wherequery.append(mTitle);
            wherequery.append("'");

           mDownloadCursor =mContext.getContentResolver().query(Downloads.CONTENT_URI, new String[] {Downloads.TITLE, Downloads.STATUS, Downloads.CURRENT_BYTES，}, wherequery.toString(), null,orderBy)；        
            int mSizeColunmId=mDownloadCursor.getColumnIndexOrThrow(Downloads.CURRENT_BYTES);   
           mDownloadCursor.moveToFirst();    
            int size=mDownloadCursor.getInt(mSizeColunmId);
       ｝
｝
  4：如何刪除下載記錄
    private void deleteHistory(String title)//刪除掉指定名稱的下載記錄
    { 
        StringBuilder whereDelete = new StringBuilder(Downloads.TITLE);
        whereDelete.append("=");
        whereDelete.append("'");
        whereDelete.append(str);
        whereDelete.append("'");
        this.getContentResolver().delete(Downloads.CONTENT_URI,whereDelete.toString(), null);

    }   

二、利用API提供的DownloadManager類實現(Since API 9)：

  DownloadManger mgr=(DownloadManager)getSystemService(DOWNLOAD_SERVICE);   // 加入到下載隊列：
 

  

  
 Request dwreq=new DownloadManager.Request(uri); 
  
 
  
        dwreq.setTitle("Demo"); 
  
        dwreq.setDescription("android-ndk-r6-linux-x86.tar.bz2"); 
  
        dwreq.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,"android-ndk-r6-linux-x86.tar.bz2"); 
  
        dwreq.setNotificationVisibility(0); 
  
        dwreq.setShowRunningNotification(true); 
  
 
  
        lastDownload=mgr.enqueue(dwreq); 

 
// 查詢下載的狀態

public void queryDownloadStatus(View v)  { 
 
      Runnable queryRunable = new Runnable() { 
          long totalsize=0; 
          long dowsize=0; 
          boolean downok=false; 
          Cursor c=null; 
 
        public void run() { 
 
            //查詢下載檔案總大小 
            totalsize=c.getLong(c.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES)); 
 
            Message msg_packsize=new Message(); 
            msg_packsize.what=MSG_DWPACKSIZE; 
            msg_packsize.arg1=(int) totalsize; 
            handler.sendMessage (msg_packsize); 
 
            while(downok==false){ 
                         c=mgr.query(new DownloadManager.Query().setFilterById(lastDownload)); 
 
                        if (c==null) { 
                            //tvdwsize.setText("query=null"); 
                        } 
                        else { 
                            c.moveToFirst(); 
                            //查詢已經下載的大小 
                            dowsize=c.getLong(c.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR)); 
                            if(totalsize==dowsize) downok=true; 
                        } 
 
                        Message msg=new Message(); 
                        msg.what=MSG_DWSIZE; 
                        msg.arg1=(int) dowsize; 
                        handler.sendMessage (msg); 
 
                        try { 
                            Thread.sleep(5000); 
                        } catch (InterruptedException e) { 
                            // TODO Auto-generated catch block 
                            e.printStackTrace(); 
                        } 
                        c.close(); 
                } 
            }//run 
        }; 
 
           Thread background = new Thread(queryRunable); 
           background.start(); 
} 
 
    public void delDownloads(View view) { 
 
        Toast.makeText(this, "delDownloads", Toast.LENGTH_LONG).show(); 
        mgr.remove(lastDownload); 
 
 
   }