Wsrtjtyk

I´m new in the bloc pattern and stream stuff. I want to show up an alert dialog when I press a button, but I can´t find a way to do it. Actually my code is:

Widget button() {

  return RaisedButton(

      child: Text('Show alert'),

      color: Colors.blue[700],

      textColor: Colors.white,

      onPressed: () {

        bloc.submit();

      });

   }







return Scaffold(

        appBar: AppBar(

          title: Text("Title"),

        ),

        body: StreamBuilder(

            stream: bloc.getAlert,

            builder: (context, snapshot) {

              if (snapshot.hasData) {

                return Text("I have Dataaaaaa ${snapshot.data}");

              } else

                return ListView(

                  children: <Widget>[

                    Container(

                     button()

                    )

                ...

And the BLoC:

final _submissionController = StreamController();

Stream get submissionStream=> _submissionController.stream;

Sink get submissionSink=> _submissionController.sink;

I tried to do something like:

Widget button() {

  return StreamBuilder(

stream: submissionStream

builder: (context, snapshot){

if (snapshot.hasData){

return showDialog(...)

}else

 return RaisedButton(

      child: Text('Show alert'),

      color: Colors.blue[700],

      textColor: Colors.white,

      onPressed: () {

        bloc.submit();

      });

   }

But, of course, it didn´t work.

You can't show a dialog when build working. When you have new data, then you create a new widget. Probably better for you will be not using the stream in this case, but if it necessary you should use

WidgetsBinding.instance.addPostFrameCallback((_) => yourFunction(context));

in your if

if (snapshot.hasData) {
WidgetsBinding.instance.addPostFrameCallback((_) => showDialogFunction(context));
}

This code will be launched after build method, so dialog will show immediately.

Bloc function always return widget, so always return button() or different wiget when stream has data

Here is what I did, it might be wrong as I'm also new to flutter. But works for my scenario.

Widget build(BuildContext context) {

final authBloc = BlocProvider.of<AuthBloc>(context);



authBloc.outServerResponse.listen((serverResponse) {

  if (serverResponse.status == 'success') {

    _navigateToLogin();

  } else {

    _showSnakBar(serverResponse.message);

  }

});

.... Rest of the code which returns the widget, 

which in my case is form widget with button for submitting as follows,

onPressed: () {

  if (_formKey.currentState.validate()) {

      _formKey.currentState.save();

      authBloc.processRegister.add(_registrationData.toMap());

  }

}

outServerResponse is the stream that outputs after finishing API POST call.

authBloc.processRegister is the input sink to pass form data to my Auth API Service Provider.

_nagivateToLogin & _showSnakBar are simple functions

_navigateToLogin() {

      Navigator.of(context).pop();

}



_showSnakBar(String msg) {

     Scaffold.of(context).showSnackBar(

      SnackBar(

        content: Text(msg),

      ),

     );

 }