Flutter: Set global variable using OK button on AlertDialog in StatefulBuilder

Question

How to set global variable using OK button on AlertDialog in StatefulBuilder?

String stringMain = "My String";

Future<String?> dialogChangeMainContent(BuildContext context) {
    return showDialog<String>(
        context: context,
        builder: (BuildContext context) {
          return StatefulBuilder(builder: (context, setState) {
            return AlertDialog(
              title: const Text('AlertDialog Title'),
              content: const Text('AlertDialog description'),
              actions: <Widget>[
                TextButton(
                  onPressed: () {
                    Navigator.pop(context, 'OK');
                    setState(() {
                      // setState2();
                      stringMain = "New String";
                    });
                  },
                  child: const Text('OK'),
                ),
              ],
            );
          });
        });
  }

I changed StatefulWidget from StatelessWidget, but nothing changes. What I know is the problem is because the button is in the StatefulBuilder. If using BLoC etc, it's too wasteful for only small applications.

Answer 1

I found a way to solve my problem, redrawing (refreshing) the Text (or other widget) in a Stateless Widget from an AlertDialog in a StatefulBuilder. By creating a setState with a different name, for example setStateTarget. Without having to rebuild the entire page, or without state management like BLoC. My code:

String stringMain = "My String";

@override
  Widget build(BuildContext context) {
    return Column(
      // ....
      children: [
        StatefulBuilder(builder: (BuildContext context, setStateTarget) {
          return Column(children: [
            Text(stringMain), //  <--- target
            TextButton(
                onPressed: () => dialogChangeMainContent(context, setStateTarget),
                child: const Text('Show Dialog'))
          ]);
        })
      ],
    );
  }

  Future<String?> dialogChangeMainContent(BuildContext context, StateSetter setStateTarget) {
    return showDialog<String>(
                  context: context,
                  builder: (BuildContext context) {
                    return StatefulBuilder(builder: (context, setState) {
                      return AlertDialog(
                        title: const Text('AlertDialog Title'),
                        content: const Text('AlertDialog description'),
                        actions: <Widget>[
                          TextButton(
                            onPressed: () {
                              Navigator.pop(context, 'OK');
                              setStateTarget(() {
                                // setState2();
                                stringMain = "New String";
                              });
                            },
                            child: const Text('OK'),
                          ),
                        ],
                      );
                    });
                  });
  }