Can a StreamBuilder be outside the build method?

Question

I can't find any information on where the StreamBuilder needs to be within the code so I am asking here.

I have a screen in my flutter app that has a lot of input textfields. Each textfield has this code structure:

TextField(
                  keyboardType: TextInputType.text,
                  controller: clientLNameController,
                  textAlign: TextAlign.center,
                  onChanged: (value) {
                    trxnProvider.changeclientLName(value);
                  },
                  decoration: kTextFieldDecoration.copyWith(
                      hintText: 'Client Last Name',
                      labelText: 'Client Last Name'),
                ),

In the initState() function I call a method that pulls data from a Firestore collection and populates the TextEditingController associated with each textfield.

@override
  void initState() {
    getTrxn();
  }

It is in this function that I try to get the data using a StreamBuilder. Here is the code.

getTrxn() async {
    StreamBuilder (
        stream: _db.collection('agency').doc(globals.agencyId).
        collection('trxns').doc(globals.currentTrxnId).snapshots(),
        builder: (BuildContext context, AsyncSnapshot trxnSnapshot) {
          if (trxnSnapshot.hasData) {
            clientFNameController.text = trxnSnapshot.data['clientFName'] ?? "";
          }
    )
    return SizedBox.shrink();
}

The problem I am having is when I run the code through the debugger and try to step through the code I get to the line StreamBuilder and then I am taken out of the function. None of the code inside the StreamBuilder gets executed but there is no error either.

I am thinking that I can not use a StreamBuilder outside the "build" function.

@override
  Widget build(BuildContext context) {

Is this correct or am I missing something else?

Answer 1

Do it like this

  late final StreamSubscription myStream;

  @override
  void initState() {
    myStream = _db
        .collection('agency')
        .doc(globals.agencyId)
        .snapshots()
        .listen((snapshot) => clientFNameController.text = snapshot.data()?['clientFName'] ?? "");
    super.initState();
  }

Make sure to dispose the stream once done

  @override
  void dispose() {
    myStream.cancel();
    super.dispose();
  }