How to pass data from a child Stateful widget to Parent Widget in Flutter

user_17311927 0
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I have a Stateful widget 'DayPicker' in my flutter application. Code for the same is:

class DayPicker extends StatefulWidget {
  @override
  _DayPickerState createState() =>
      _DayPickerState();
}

class _DayPickerState extends State<DayPicker> {
  final values2 = List.filled(7, false);
  @override
  Widget build(BuildContext context) {
    var ht = MediaQuery.of(context).size.height;
    return Column(
      mainAxisSize: MainAxisSize.min,
      children: <Widget>[
        SizedBox(
          height: ht / 40,
        ),
        Text(
          'Selected Day(s): ${valuesToEnglishDays(values2, true)}',
          style: TextStyle(fontSize: ht / 40, fontStyle: FontStyle.italic),
        ),
        WeekdaySelector(
          onChanged: (v) {
            setState(() {
              values2[v % 7] = !values2[v % 7];
            });
          },
          values: values2,
          selectedFillColor: Colors.amber,
          selectedColor: Colors.black,
          selectedShape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(5),
          ),
          shape: RoundedRectangleBorder(
            side: BorderSide(color: Colors.red.withOpacity(0.5)),
            borderRadius: BorderRadius.circular(25),
          ),
        ),
      ],
    );
  }
}

This widget is used to select the days of week as shown here:

enter image description here

I want the list of days to be passed into my Parent widget i.e the widget using DayPicker(), so that I can store this list to Firebase Firestore. How can I do this? In case of Stateless widget there is a method to pass data from child to parent using callback but I wonder how to pass data in this case.

google-cloud-firestore flutter widget
1 Answers

You can also use callback to handle in this case. You need to use it like widget.callback(value) where it is changing data on child. Run the bellow snippet and do a check yourself.


class AppX extends StatefulWidget {
  final String province;
  const AppX({
    Key? key,
    required this.province,
  }) : super(key: key);

  @override
  State<AppX> createState() => _AppXState();
}

class _AppXState extends State<AppX> {
  double? sliderValue;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: [
          Text("${sliderValue ?? 0}"), //handling null using defaul value
          Child(
            callback: (p0) {
              setState(() {
                sliderValue = p0;
              });
            },
          )
        ],
      ),
    );
  }
}

class Child extends StatefulWidget {
  const Child({
    Key? key,
    required this.callback,
  }) : super(key: key);

  final Function(double) callback;

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

class _ChildState extends State<Child> {
  double _sliderValue = 0;

  @override
  Widget build(BuildContext context) {
    return Slider(
      value: _sliderValue,
      onChanged: (value) {
        widget.callback(value);
        setState(() {
          _sliderValue = value;
        });
      },
    );
  }
}
user_101571270
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