title: flutter_downloader auto open file when complete
body: <p>so I'm trying to work with download manager in flutter using flutter_downloader package. I manage to make my app download the file I wanted. How can I make my app more advance ? I wanted my app to be able to open the downloaded file automatically when the download is done.</p>
  <p>Another question is, if I already download the file first time how can I make the button trigger to open the file location rather than downloading the file again ?</p>
  <p>Here's my current code:</p>
  <pre><code>  TextButton(
      child: Text(
        ticketData['file_attachment_map'][index]['name'],
        style: primaryColor600Style.copyWith(fontSize:14.sp),
      ),
      
      onPressed: () async {
        final permissionStatus = await Permission.storage.request();
      
        if (permissionStatus.isGranted) {
        final externalDir = await getExternalStorageDirectory();
      
        final taskId =await FlutterDownloader.enqueue(
          url: ticketData['file_attachment_map']
          [index]['url'],
          savedDir:externalDir!.path,
          showNotification:true,
          openFileFromNotification:true,
          );
        } else {
          print('Permission denied');
        }
      },
    ),
  </code></pre>