Flutter using Uint8List in FutureBuilder is giving error

Question

I'm building a flutter gallery app from this reference Flutter Image Gallery

All works fine but I'm getting error inside Future Builder

This is the error warning I'm getting

The name 'Uint8List' isn't a type so it can't be used as a type argument.
Try correcting the name to an existing type, or defining a type named 'Uint8List'.

And this is the runtime error I'm getting

Error: 'Uint8List' isn't a type.
    return FutureBuilder<Uint8List>(
                         ^^^^^^^^^

This Uint8List is totally new concept for me, don't know what to do.

This is the widget that returns a Future Builder

  @override
  Widget build(BuildContext context) {
    // We're using a FutureBuilder since thumbData is a future
    return FutureBuilder<Uint8List>(
      future: asset.thumbData,
      builder: (_, snapshot) {
        final bytes = snapshot.data;
        // If we have no data, display a spinner
        if (bytes == null) return CircularProgressIndicator();
        // If there's data, display it as an image
        return InkWell(
          onTap: () {
            // TODO: navigate to Image/Video screen
          },
          child: Stack(
            children: [
              // Wrap the image in a Positioned.fill to fill the space
              Positioned.fill(
                child: Image.memory(bytes, fit: BoxFit.cover),
              ),
              // Display a Play icon if the asset is a video
              if (asset.type == AssetType.video)
                Center(
                  child: Container(
                    color: Colors.blue,
                    child: Icon(
                      Icons.play_arrow,
                      color: Colors.white,
                    ),
                  ),
                ),
            ],
          ),
        );
      },
    );
  }

I've search it on google but doesn't get any satisfied answer. Thanks in advance.

Solution 1

try this solution:

FutureBuilder<Uint8List>

to

FutureBuilder<dynamic>

or

FutureBuilder<List<int>>

Solution 2

Just leave out the type, the compiler is smart enough to infer that from the type of Future<> you provide:

FutureBuilder(
    future: asset.thumbData,

Comments

[nvoigt]

Why do you use a type there at all?

[Harshvardhan Joshi]

I think the import is missing from your code, add this (package)[pub.dev/packages/typed_data] in the pubspec & try again by importing the (typed_data)[pub.dev/documentation/typed_data/latest].

[You and the web]

@nvoigt I just refer to an article. It returns a Future<Uint8List> representing the actual bytes of the thumbnail

[nvoigt]

Why do you think a type needs to be explicitly given there at all?

[You and the web]

Yes the dynamic work for me but i prefer to @HarshvardhanJoshi's comment by importing typed_data. Thanks for the answer.

[You and the web]

Yes i appreciate your answer. Can you please briefly explain that why we should not need <Uint8List>

[nvoigt]

I indirectly already did. It is called "type inference", most languages can do that. If you have for example a method method<T>(T t), then when you pass in an int, you can just do method(5) instead of method<int>(5) because the compiler already inferred from your usage that you mean int. See dart.dev/guides/language/type-system#type-inference