Question 75404 in Flutter Question posted in
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Flutter: The function setState isn't defined and I am using a Stateful widget

I’ll put the code briefly to show how everything is meant to flow from the Stateful widget.

I basically want the checkbox on my card to change state when the user clicks on it.

Error message: The function ‘setState’ isn’t defined.

I did my research and I know it only works under a stateful widget. My widget tree is under a StatefulWidget so it should work but isn’t.

class MyAppState extends StatefulWidget{

       Scaffold{
          //calls CardWidget to build individual cards for my list
       }       
}

     Widget CardWidget{

          Return Inkwell {
              Container{
                   
                        child: Checkbox(
                             value: item.checkBox,
                             onChanged: (bool? value) {
                             item.checkBox = !value!;

                             setState(() {
                             item.checkBox;
                             });
                           },
                       ),
Tags:

3

Answers


  1. 0

    This will be the widget structure

    class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  var item; // the place you like

  Widget CardWidget() {
    return InkWell(
      onTap: () {},
      child: Container(
        child: Checkbox(
          value: item.checkBox,
          onChanged: (bool? value) {
            item.checkBox = !value!;

            setState(() {
              item.checkBox;
            });
          },
        ),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold();
  }
}

    More about StatefulWidget

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  2. 0

    You should put the CardWidget inside a class that extends StatefulWidget:

    class CardWidget extends StatefulWidget {
  final Item item;

  CardWidget(this.item);

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

class _CardWidgetState extends State<CardWidget> {
  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: () {
        setState(() {
          widget.item.checkBox = !widget.item.checkBox;
        });
      },
      child: Container(
        child: Checkbox(
          value: widget.item.checkBox,
          onChanged: (bool? value) {
            setState(() {
              widget.item.checkBox = !value!;
            });
          },
        ),
      ),
    );
  }
}

    now with _CardWidgetState you can use setState.

    happy coding….

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  3. 0

    CarWidget() has to be written liket this:

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

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

class _CardWidgetState extends State<CardWidget> {
  @override
  Widget build(BuildContext context) {
    return InkWell(child: 
      Container(child:
       Checkbox(
       value: item.checkBox,
        onChanged: (bool? value) {
         item.checkBox = !value!;

         setState(() {
            item.checkBox;
         });
       },
       ),
      ),
    );
  }
}
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