Initial value on TextField with StreamBuilder - flutter

Question

I have a TextField rendered with the help of a StreamBuilder, following the BLoC pattern with a sink and stream.
Widget field(SignUpBloc signUpBloc) {
return StreamBuilder(
stream: signUpBloc.outFirstName,
builder: (context, snapshot) {
return TextField(
style: TextStyle(fontSize: 15.0),
onChanged: signUpBloc.inFirstName,
decoration: InputDecoration(
errorStyle: TextStyle(fontSize: 15.0),
errorText: snapshot.error
),
);
},
);
}
My question is how do I set up an initial value? I've tried with the StreamBuilder's initialData property but no text appears in the TextField.

Answer 1

TextEditingController _controller = TextEditingController(); // make a controller,
Widget field(SignUpBloc signUpBloc) {
return StreamBuilder(
stream: signUpBloc.outFirstName,
initialData: YourData, // provide initial data
builder: (context, snapshot) {
_controller.value = TextEditingValue(text: "${snapshot.data}"); // assign value to controller this way
return TextField(
controller: _controller,
style: TextStyle(fontSize: 15.0),
onChanged: signUpBloc.inFirstName,
decoration: InputDecoration(
errorStyle: TextStyle(fontSize: 15.0),
errorText: snapshot.error
),
);
},
);
}
Edit: To put the cursor at the end of the line, you can use
var cursorPos = _controller.selection;
if (cursorPos.start > _controller.text.length) {
cursorPos = TextSelection.fromPosition(TextPosition(offset: _controller.text.length));
}
_controller.selection = cursorPos;
Source

Answer 2

You will have to have a TextEditingController when you need to pass initial values. Using the value.copyWith strategy there is no need to deal with the cursor, and to make the widget cleaner you can pass the text controller as a parameter.
// Stream widget
Widget field(SignUpBloc signUpBloc, TextEditingController _txtController) {
return StreamBuilder(
stream: signUpBloc.outFirstName,
builder: (context, snapshot) {
_txtController.value =
_txtController.value.copyWith(text: snapshot.data);
return TextField(
controller: _txtController,
onChanged: signUpBloc.inFirstName;
decoration: InputDecoration(
errorStyle: TextStyle(fontSize: 15.0),
errorText: snapshot.error
),
});
}