How to update global variable from inside a function?-CodePudding

I want to change the value of RowIndex from _getAttendence

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

  @override
  State<Attendence> createState() => _AttendenceState();
}

class _AttendenceState extends State<Attendence> {
  String RowIndex = "0";
Widget build(BuildContext context){...}
 _getAttendence(String KEY, String RowIndex) async {
          RowIndex = "50";
   }
}

CodePudding user response：

First option is to create a global variable inside the class like this:

// 'a' can also be placed here :)
class MyPage extends StatefulWidget {
  const MyPage({Key? key}) : super(key: key);

  @override
  State<MyPage> createState() => _MyPageState();
}

// this is a global variable. It has no colors. (see image)
double a = 20.0;
/*
  now, wherever you import the file containing the class 'MyPage',
  you can use this variable!
 */

class _MyPageState extends State<MyPage> {
  
  // this is a local variable. It has a purple color. (see image)
  double b = 10.0;
  
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

Second option is to create a dart file, let's call it globals.dart. Then, in this file define your variables, double a = 10.0; And then in your other dart files you can either import it as before and use the variables or you can use this: in your other files use: import: 'globals.dart' as globals; and then in your file you can use: globals.a = 20.0; inside a setState(()=>{});. Don't forget to setState above as well :)

CodePudding user response：

RowIndex is not global, it's class wide, it's nested in your State object, if you want to make it global, put it outside the class tag, you could do this

    @override
    State<Attendence> createState() => _AttendenceState();
  }

    class _AttendenceState extends State<Attendence> {
  String RowIndex = "0";

  _getAttendence(String KEY, String RowIndex) async {
    for (var q in (aList as List)) {
      AttendenceList innerAttendence = AttendenceList(
          q["RowIndex"],
          q["Id"],
          q["InText"],
          q["OutText"],
          q["InDate"],
          q["Duration"],
          q["DateBGColorHEX"],
          q["InColorHEX"],
          q["OutColorHEX"],
          q["DurationColorHEX"]);
      FetchList.add(innerAttendence);
    }
    setState(() {
      RowIndex = FetchList[FetchList.length - 1].RowIndex.toString();
    });
  }
  
  @override
  void initState() {
    if (controller.position.maxScrollExtent == controller.offset) {
      _getAttendence(KEY!, RowIndex);
    }
    super.initState();
  }
}