The argument type 'Object?' can't be assigned to the parameter type 'FutureOr<Uint8List>?'


How to solve this error? Error message: The argument type ‘Object?’ can’t be assigned to the parameter type ‘FutureOr<Uint8List>?’.

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My code


  Future<Uint8List> _getBlobData(html.Blob blob) {
    final completer = Completer<Uint8List>();
    final reader = html.FileReader();
    reader.onLoad.listen((_) => completer.complete(reader.result));
    return completer.future;


FileReader.result returns an Object? because it could return a Uint8List, a String, or null. If you can guarantee that reader.result is a Uint8List, just perform a cast:

reader.onLoad.listen((_) => completer.complete(reader.result! as Uint8List));

Otherwise you should check the type of reader.result first. For example:

reader.onLoad.listen((_) {
  var result = reader.result;
  if (result is Uint8List) {
  } else {
      Exception('Unexpected result type: ${result.runtimeType}'));

Answered By – jamesdlin

Answer Checked By – Gilberto Lyons (FlutterFixes Admin)

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