Change an entire Scaffold body

Question

Hello!

I’m trying to finalize an app, but I stopped in a problem.

I have a screen with a Scaffold and a action in appBar with widget that returns the date.

I would like to know how to update a text with the date inside the body. I know it can be updated. Yeah, I can print it and see it changes the value but I can’t change the text.

data file.Dart

class Data extends StatefulWidget {
  @override
  _DataState createState() => _DataState();
}

class _DataState extends State<Data> {
  StoreChamada testeData = StoreChamada();
  DateTime selectDate = DateTime.now();

  Future<Null> _selectdate(BuildContext context) async {

    final DateTime picked = await showDatePicker(
        context: context,
        initialDate: selectDate,
        firstDate: DateTime(2000, 1),
        lastDate: DateTime(2050));
    testeData.setData(DateFormat('dd-MM').format(picked));
    if (picked != null && picked != selectDate)
      setState(() {

        selectDate = picked;

      });
  }
  @override
  Widget build(BuildContext context) {
    var data = DateFormat('dd-MM').format(selectDate);
    return Row(children: <Widget>[
      Text(data + '  '),
      IconButton(
        icon: Icon(IconData(59670, fontFamily: 'MaterialIcons')),
        onPressed: () {
          setState(() {
            _selectdate(context);
          });
        },
      )
    ]);
  }
}

function I call to update the value of the variable sdata with the date I use on the body.

void setData(value) => sdata = value;

list screen that has the text.

 body: Container(
          child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Text(sdata == null
              ? '${DateFormat('dd-MM').format(DateTime.now())}'
              : sdata),

I tried several things, I thought about using a setstate(){} on the body but I don’t even know if that would be possible. Anyway, if anyone can help.

That’s the screen I’d like to change. I have a widget with text and date that are updated as soon as I change the date, but I can’t update the yellow part which is where the data I update is located depending on the date. The date value is changed but the screen does not update, only when I hotreload.

Answer 1

I’m not sure I understand your problem, but if you need to pass some data from a child widget to a priest, there are different ways to do this, but the simplest is to simply pass a function to the child widget that will be called every time you want to run some code, something like:

Your child widget receives the function as a constructor parameter and will call it every event:

class SelectDate extends StatelessWidget {
  SelectDate({Key key, this.onChange}) : super(key: key);
  
  final Function(DateTime) onChange;
  
  @override
  Widget build(BuildContext context) {
    return IconButton(
        icon: Icon(Icons.calendar_today),
        onPressed: () {
          onChange?.call(DateTime.now());
        },
      );
  }
}

And then in your Parent Widget, in your Scaffold, when you create your Child Widget:

Scaffold(
  appBar: AppBar(
    title: Text(widget.title),
  ),
  body: Center(
    child: Column(
      children: [
        SelecteDate(
          onChange: (data) {
            /// Faça algo com a nova data
          }
        )
      ]
    ),
  ),
);

If this was your problem, it can be solved so anyway I saw that you are making unnecessary use of the method setState, I suggest you take a look at documentation about what these methods do and how to use them to your advantage. There are also several tutorials on the Flutter channel on youtube, one of which may be interesting for your case is the Inheritedwidget. And also Future<Null> where Null is not a valid type, if you have nothing to return from this function the correct is Future<void>