how to get value in textfield flutter

Question

how to enter value into textfield ? i have the value i get from api, that is name data here i edit the data and then want to update the contents of the data. but I'm still confused about initializing the data if it doesn't edit the data

I attach the code:

class ProfileData extends StatefulWidget {
  @override
  _ProfileDataState createState() => _ProfileDataState();
}

class _ProfileDataState extends State<ProfileData> {

  TextEditingController fnameController = TextEditingController(text: '');
  
bool isLoading = false;

  @override
  Widget build(BuildContext context) {

    UserProvider user = Provider.of<UserProvider>(context);
    //here i call api using provider, if I print it will produce a value which is a name 'alu card' , ex : user.user.fname -> value('alu card')

    handleSubmit() async {
      setState(() {
        isLoading = true;
      });

      if (await user.submit( //method put to service
        fname: fnameController.text,
      )) {
        Navigator.pushNamed(context, '/main');
      } else { 
       print('err');
      }

      setState(() {
        isLoading = false;
      });
    }

   Widget input() {
      return Container(
        child: Column(
          children: [
            Expanded(
                child: TextFormField(
              style: blackTextStyle,
              controller: fnameController,
              decoration: InputDecoration.collapsed(
                hintText: user.user.fname, // this value 'alucard'
                hintStyle: blackTextStyle,
              ),
            ))
          ],
        ),
      );
     ....... //widget button submit 
     .......
      onpress : handleSubmit
    }

    return Scaffold(
      backgroundColor: Colors.white,
      body: input(),
    );
  }
}

Answer 1

Try out below answer I added line for getting value on Textfield

class _ProfileDataState extends State<ProfileData> {

  TextEditingController fnameController = TextEditingController(text: '');
  
bool isLoading = false;

  @override
  Widget build(BuildContext context) {

    UserProvider user = Provider.of<UserProvider>(context);
    fnameController.text = user.user.fname  // Added this line here.

    handleSubmit() async {
      setState(() {
        isLoading = true;
      });

      if (await user.submit( //method put to service
        fname: fnameController.text,
      )) {
        Navigator.pushNamed(context, '/main');
      } else { 
       print('err');
      }

      setState(() {
        isLoading = false;
      });
    }

   Widget input() {
      return Container(
        child: Column(
          children: [
            Expanded(
                child: TextFormField(
              style: blackTextStyle,
              controller: fnameController,
              decoration: InputDecoration.collapsed(
                hintText: user.user.fname, // this value 'alucard'
                hintStyle: blackTextStyle,
              ),
            ))
          ],
        ),
      );
     ....... //widget button submit 
     .......
      onpress : handleSubmit
    }

    return Scaffold(
      backgroundColor: Colors.white,
      body: input(),
    );
  }
}