Flutter, stream builder returns null

Question

I tried getting input(string) from the user using textfield, adding the input in stream, and printing the string on a different screen, but instead of the string stream builder is printing null, I understood, it's because stream doesn't have any data. But I added data in stream once the user types out something in textfield and hit save.How do I love this

Stream

StreamController NameStream = StreamController.broadcast();

Adding data to stream

textField()
textbuttion(
 onPressed: () {
                  addNStream() {
                    NameStream.sink.add(TextController);
                  }

                  setState(() {
                    addNStream();
                  });

)

Printing data in different screen

Scaffold(
  body: Container(
      child: StreamBuilder(
    stream: NameStream.stream,
    builder: (context, snapshot) {
      return Center(
        child: Text(
          snapshot.data.toString(),
          style: const TextStyle(fontSize: 40),
        ),
      );
    },
  )
  ),
)

you need to setup StreamBuilder.initialData or check snapshot.connectionState / snapshot.hasData (see StreamBuilder official docs - they have some examples on how to do that) — pskink
– pskink, Commented Mar 26, 2022 at 6:53

Randal Schwartz · Accepted Answer · 2022-03-28 18:14:45Z

2

Looks like you're using a broadcast stream. Items added to a broadcast stream when nothing is listening are silently discarded.

answered Mar 28, 2022 at 18:14

Randal Schwartz

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1 Comment

Ganesh Sivakumar Over a year ago

Could you please explain it with code

ilyes chicha · Accepted Answer · 2022-09-03 00:44:52Z

1

when you are using broadcast() your StreamBuilder don't listen to the data in the NameStream.stream in the initialization.

because the NameStream.stream doesn't have any listeners so StreamBuilder assume that the is no data so he doesn't check, this is the reason for the null.

to solve the problem you need to add listener (initSatate) before you add the event to the stream this will allow StreamBuilder to recognize that there is data in the stream.

answered Sep 3, 2022 at 0:44

ilyes chicha

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