It's my code:

 late Future<File> _imageFile; //define 

 body: FutureBuilder(
        future: _imageFile,
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done &&
              snapshot.data != null &&
              _imageFile !=null) {
            fileList.add(snapshot.data as File);
            _imageFile =null as Future<File>;
          }
          return _bodyWidget();
        },
      ),

when I run the project , is throw error: LateInitializationError: Field '_imageFile@767230325' has not been initialized.

But , how can I initialize the later variable?

and I put in this code :

  late Future<PickedFile> _imageFile ;


  @override
  void initState() {
    super.initState();
   _imageFile = ImagePicker.platform.pickImage(source: ImageSource.gallery) as Future<PickedFile>;
  }

It throwed

The following _CastError was thrown building Builder:
type 'Future<PickedFile?>' is not a subtype of type 'Future<PickedFile>' in type cast

CodePudding user response：

You can initialize your code in the initstate of StatefulWidget, like so.

class Testing extends StatefulWidget {
  const Testing({Key? key}) : super(key: key);

  @override
  _TestingState createState() => _TestingState();
}

class _TestingState extends State<Testing> {
  late Future<Your_type> myFuture;

  @override
  void initState() {
    super.initState();
    myFuture = YourQueryMethod;
  }

  @override
  Widget build(BuildContext context) {
   
  }
}

CodePudding user response：

Following the answer of IcyHerrscher and reading the error I assume you forgot that Dart 2.0 has nullability and you forgot a type T is not the same as T?

type 'Future<PickedFile?>' is not a subtype of type 'Future<PickedFile>' in type cast

so just add ? to the type you want to cast

late Future<PickedFile?> _imageFile; /// add the ? so the result of the method ImagePicker.platform.pickImage is of the same type

@override
  void initState() {
    super.initState();
   _imageFile = ImagePicker.platform.pickImage(source: ImageSource.gallery);
  }