下载管理器的回复

您需要BroadcastReceiver注册DownloadManager.ACTION_DOWNLOAD_COMPLETE：

    BroadcastReceiver receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {
                long id = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, 0);
                Query query = new Query();
                query.setFilterById(id);
                Cursor c = dm.query(query);
                if (c.moveToFirst()) {
                    int columnIndex = c.getColumnIndex(DownloadManager.COLUMN_STATUS);
                    if (DownloadManager.STATUS_SUCCESSFUL == c.getInt(columnIndex)) {
                        // TODO файл успешно загружен 
                        // здесь можно начинать
                        // с ним работать
                    }
                }
             }
         }
    };        

    context.registerReceiver(receiver, new IntentFilter(
                         DownloadManager.ACTION_DOWNLOAD_COMPLETE));