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

_downloadFile2 = () => {
  let DownloadDir = RNFetchBlob.fs.dirs.DownloadDir
  let options = {
    fileCache: true,
    addAndroidDownloads : {
      useDownloadManager : true,
      notification : true,
      title : "file name",
      path: DownloadDir + '/' + "fileName"+ '.' + 'pdf',
      description : 'download fileName'
    }
  }
  RNFetchBlob.config(options)
  .fetch('GET', 'link....')
  .catch((err) => {console.warn('error' + err)})
};