The argument type 'Widget' can't be assigned to the parameter type 'PreferredSizeWidget?'

Question

class DetailChatPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    Widget header() {
      return PreferredSize(
        preferredSize: Size.fromHeight(70),
        child: AppBar(
          backgroundColor: backgroundColor1,

        ),
      );
    }

    return Scaffold(
      backgroundColor: backgroundColor3,
      appBar: header(),
    );
  }
}

i get an error in my code that is The argument type 'Widget' cannot be set to the parameter type 'PreferredSizeWidget?' how to solve this

Solution 1

This happens because you declared your header method with the type Widget. You should instead declare it with the type PreferredSizeWidget.

PreferredSizeWidget header() {
  return PreferredSize(
    preferredSize: Size.fromHeight(70),
    child: AppBar(
      backgroundColor: backgroundColor1,
    ),
  );
}

Solution 2

change

Widget header() {
  return PreferredSize(
    preferredSize: Size.fromHeight(70),
    child: AppBar(
      backgroundColor: backgroundColor1,

    ),
  );
}

to

PreferredSize header() {
  return PreferredSize(
    preferredSize: Size.fromHeight(70),
    child: AppBar(
      backgroundColor: backgroundColor1,

    ),
  );
}