modal bottom sheet reusable class missing "State build" method

I am trying to create a custom bottom sheet class to be re-usable, but it gives me the error of missing "State build" method. I know that I may include the @override method, but I have checked other responses like this, and I did not see the build method.

class ModalBottomSheet extends StatefulWidget {
  final Function()? onPressed;

  const ModalBottomSheet({Key? key, this.onPressed}) : super(key: key);

  @override
  State<ModalBottomSheet> createState() => _ModalBottomSheetState();
  }
  
  //error here 
  class _ModalBottomSheetState extends State<ModalBottomSheet> {
   modal(context){
    showModalBottomSheet(
        context: context,
        isScrollControlled: true,
        backgroundColor: Colors.transparent,
        builder: (BuildContext context) {
          return Container(
           
            ),
          );
        });
      }
    }

EDIT:

class ModalBottomSheet {
void modal(context) {
Function(int)? onPressed;

showModalBottomSheet(
    context: context,
    isScrollControlled: true,
    backgroundColor: Colors.transparent,
    builder: (BuildContext context) {
      return Container(
        height: 200,
        decoration: BoxDecoration(
          color: Colors.white,
          borderRadius: BorderRadius.only(
              topLeft: Radius.circular(20), topRight: Radius.circular(20)),
        ),
        child: Padding(
          padding: EdgeInsets.all(10),
          child: Column(
            children: [
          TextButton(
                onPressed: (1) {
                  onPressed?.call();
                },
                child: Text(
                  'CAMERA',
                ),
              ),
              
              TextButton(
                onPressed: (2) {
                  onPressed?.call();
                },
                child: Text(
                  'GALLERY',
                ),
              ),

This is the Main screen where to show the custom modal sheet:

ModalBottomSheet.modal(context,
                          onPressed: (index){
                            if(index == 1){
                              pickImage(ImageSource.camera);
                            }else{
                              pickImage(ImageSource.gallery);
                            }
                          });
   

You are extending the StatefulWidget, which requires you to override the build method. Instead, you can create a class or mixin that doesn't extend Widget, it will have a method that shows modal and requires BuildContext as a function parameter.

class ModalBottomSheet {
  void modal(context) {
    showModalBottomSheet(
      context: context,
      isScrollControlled: true,
      backgroundColor: Colors.transparent,
      builder: (BuildContext context) {
        return ...
      },
    );
  }
}

Edit:

You can also pass other parameters to this function, as void Function()? onPressed.

class ModalBottomSheet {
  static void modal(BuildContext context, void Function()? onPressed) {
    showModalBottomSheet(
      context: context,
      isScrollControlled: true,
      backgroundColor: Colors.transparent,
      builder: (BuildContext context) {
        return ...;
      },
    );
  }
}