how to upload pdf to firebase flutter code example

Example: how to upload pdf to firbase flutter

final mainReference = FirebaseDatabase.instance.reference().child('Database');
Future getPdfAndUpload()async{
  var rng = new Random();
  String randomName="";
  for (var i = 0; i < 20; i++) {
    print(rng.nextInt(100));
    randomName += rng.nextInt(100).toString();
  }
  File file = await FilePicker.getFile(type: FileType.CUSTOM, fileExtension: 'pdf');
  String fileName = '${randomName}.pdf';
  print(fileName);
  print('${file.readAsBytesSync()}');
  savePdf(file.readAsBytesSync(), fileName);
}

Future savePdf(List<int> asset, String name) async {

  StorageReference reference = FirebaseStorage.instance.ref().child(name);
  StorageUploadTask uploadTask = reference.putData(asset);
  String url = await (await uploadTask.onComplete).ref.getDownloadURL();
  print(url);
  documentFileUpload(url);
  return  url;
}
void documentFileUpload(String str) {

  var data = {
    "PDF": str,
  };
  mainReference.child("Documents").child('pdf').set(data).then((v) {
  });
}