I am realtively new to flutter. HOW TO UPDATE a private variable inside a stateteful flutter widget from another class.

• I KNOW ONE WAY IS TO DECLARE IT GLOBALLY but THIS WILL CHANGE MANY THINGS. FOR EXAMPLE: This card is like a button. There are many buttons generated from this class. If I make _temp a global variable; i will lose the sole purpose i.e it being unique for all buttons, all categories, all foods.

• another way can be to create a method but i am not sure how t aces it from outside the widget? e.g:

  void reset() { _temp = 0; }

Please see the code to understand the problem:

class ReusableCard extends StatefulWidget {
  ReusableCard({

    required this.itemName,
  });

  final String? itemName;

  @override
  State<ReusableCard> createState() => _ReusableCardState();
}

class _ReusableCardState extends State<ReusableCard> {

 // HOW TO UPDATE THIS int _temp (BELOW) FROM ANOTHER CLASS?
 // I KNOW I CAN DECLARE IT GLOBALLY but THIS WILL CHANGE MANY THINGS.
 //  FOR EXAMPLE: This card is like abutton. There are many buttons generated from this class. If I make _temp a global variable; i will lose the sole purpose i.e it being unique for all buttons, all categories, all foods.


  int _temp = 0;
       
  @override
  Widget build(BuildCon .......

CodePudding user response：

You can do that by the following steps:

1. Make _ReusableCardState and _temp not private (i.e remove the underscore)
2. Make ReusableCard constructor takes an optional Key and calls its super constructor with this key. like this ReusableCard({Key? key, required this.itemName}) : super(key: key);
3. Define a key with the state like this final GlobalKey<ReusableCardState> reusableCardKey = GlobalKey(); in the class that calls ReusableCard
4. Pass this key to the ReusableCard like this ReusableCard(key: reusableCardKey, itemName: "First Item")
5. Now you can use this key (reusableCardKey) to modify temp through reusableCardKey.currentState.temp = 28;

CodePudding user response：

try to declare the variable as Static, like this code

void main() {
  First.name = 'Bar';
  print(First.name);
}


class First {
  static String name = 'Foo';
}