仅4行代码实现Android快速文件下载

 //创建下载任务,downloadUrl就是下载链接DownloadManager.Request request = new DownloadManager.Request(Uri.parse(downloadUrl));//指定下载路径和下载文件名request.setDestinationInExternalPublicDir("/download/", fileName);//获取下载管理器DownloadManager downloadManager= (DownloadManager) mContext.getSystemService(Context.DOWNLOAD_SERVICE);//将下载任务加入下载队列，否则不会进行下载downloadManager.enqueue(request); 

 //使用系统下载器下载private void downloadAPK(String versionUrl, String versionName) {    //创建下载任务    DownloadManager.Request request = new DownloadManager.Request(Uri.parse(versionUrl));    request.setAllowedOverRoaming(false);//漫游网络是否可以下载    //设置文件类型，可以在下载结束后自动打开该文件    MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();    String mimeString = mimeTypeMap.getMimeTypeFromExtension(MimeTypeMap.getFileExtensionFromUrl(versionUrl));    request.setMimeType(mimeString);    //在通知栏中显示，默认就是显示的    request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE);    request.setVisibleInDownloadsUi(true);    //sdcard的目录下的download文件夹，必须设置    request.setDestinationInExternalPublicDir("/download/", versionName);    //request.setDestinationInExternalFilesDir(),也可以自己制定下载路径    //将下载请求加入下载队列    downloadManager = (DownloadManager) mContext.getSystemService(Context.DOWNLOAD_SERVICE);    //加入下载队列后会给该任务返回一个long型的id，    //通过该id可以取消任务，重启任务等等，看上面源码中框起来的方法    mTaskId = downloadManager.enqueue(request);    //注册广播接收者，监听下载状态    mContext.registerReceiver(receiver,        new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));  } 

   //广播接受者，接收下载状态  private BroadcastReceiver receiver = new BroadcastReceiver() {    @Override    public void onReceive(Context context, Intent intent) {      checkDownloadStatus();//检查下载状态    }  }; 

 //检查下载状态  private void checkDownloadStatus() {    DownloadManager.Query query = new DownloadManager.Query();    query.setFilterById(mTaskId);//筛选下载任务，传入任务ID，可变参数    Cursor c = downloadManager.query(query);    if (c.moveToFirst()) {      int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));      switch (status) {        case DownloadManager.STATUS_PAUSED:          MLog.i(">>>下载暂停");        case DownloadManager.STATUS_PENDING:          MLog.i(">>>下载延迟");        case DownloadManager.STATUS_RUNNING:          MLog.i(">>>正在下载");          break;        case DownloadManager.STATUS_SUCCESSFUL          MLog.i(">>>下载完成");          //下载完成安装APK          //downloadPath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsolutePath() + File.separator + versionName;          installAPK(new File(downloadPath));          break;        case DownloadManager.STATUS_FAILED:          MLog.i(">>>下载失败");          break;      }    }  } 

   //下载到本地后执行安装  protected void installAPK(File file) {    if (!file.exists()) return;    Intent intent = new Intent(Intent.ACTION_VIEW);    Uri uri = Uri.parse("file://" + file.toString());    intent.setDataAndType(uri, "application/vnd.android.package-archive");    //在服务中开启activity必须设置flag,后面解释    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);    mContext.startActivity(intent);  }