Passing data from reusable widget to activity. (Flutter)

Question

I made a reusable widget in flutter. It is a list item but when I press on it, it should navigate to another screen in the app. The problem is, I want the title of the list item (widget.title) to be the same as the CupertinoNavigationBar. I tried to pass it like in the official documentation but I get errors like: Expected 2 arguments but instead got 1. Please help me...

Here's the code:

class Elem extends StatefulWidget {
  final String imagine;
  final String titlu;
  final String subtitlu;
  final String tip;
  final String link;

  const Elem(
      {Key key, this.imagine, this.titlu, this.subtitlu, this.tip, this.link})
      : super(key: key);

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

class _StatefulStateCupertinoTwo extends State<Elem> {
  @override
  Widget build(BuildContext context) {
    return ListTile(
      leading: ClipRRect(
        child: Image.network(
          widget.imagine,
        ),
        borderRadius: BorderRadius.circular(10.0),
      ),
      title: Text(widget.titlu, style: TextStyle(color: Colors.white)),
      subtitle: Text(widget.subtitlu, style: TextStyle(color: Colors.grey)),
      trailing: Icon(
        CupertinoIcons.add_circled_solid,
        color: CupertinoColors.systemBlue,
        size: 30,
      ),
      onTap: () {
        Navigator.push(context, CupertinoPageRoute(builder: (context) => Detaile(
          widget.titlu,
        )));
      },
    );
  }
}
class Detaile extends StatelessWidget{
  final String title;
  // receive data from the FirstScreen as a parameter
  Detaile(String titlu, {Key key, @required this.title}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return CupertinoPageScaffold(
      navigationBar: const CupertinoNavigationBar(
        middle: Text(title),
      ),
      child: Text('Hello'),
        );
  },
}

Also, here are some errors I get:

Too many positional arguments: 0 expected, but 1 found. Try removing the extra arguments.

Too many positional arguments: 2 expected, but 1 found. Try removing the extra arguments.

Undefined name 'titlu'. Try correcting the name to one that is defined, or defining the name.

Arguments of a constant creation must be constant expressions. Try making the argument a valid constant, or use 'new' to call the constructor.

Evaluation of this constant expression throws an exception.