Flutter : TextEditingController Only Static member can be accessed in initializer error - flutter

Question

I'm passing data from listmosque.dart to update_screen.dart for updating data.
Anything it's work but i want set default value of textedittingcontroller.
TextEditingController _txtnrp = TextEditingController(text: "${widget.nrpUpdate}"); <- this error
I'm getting message Only static members can be accessed in initializers. in ${widget.nrpUpdate}
How to fix this ?
It's my update_screen.dart
import 'package:flutter/material.dart';
class UpdateScreen extends StatefulWidget {
final String idUpdate;
final String nrpUpdate;
final String namaUpdate;
final String emailUpdate;
final String jurusanUpdate;
UpdateScreen(
{this.idUpdate,
this.nrpUpdate,
this.namaUpdate,
this.emailUpdate,
this.jurusanUpdate});
#override
_UpdateScreenState createState() => _UpdateScreenState();
}
class _UpdateScreenState extends State<UpdateScreen> {
TextEditingController _txtnrp = TextEditingController(text: "${widget.nrpUpdate}"); <- In this line error
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
leading: IconButton(
icon: Icon(Icons.arrow_left),
onPressed: () => Navigator.pop(context, false),
),
centerTitle: true,
title: Text('Update ${widget.namaUpdate}'),
),
body: Container(
child: Center(
child: SingleChildScrollView(
padding: EdgeInsets.all(20),
scrollDirection: Axis.vertical,
child: Column(
children: <Widget>[
TextField(
controller: _txtnrp,
keyboardType: TextInputType.number,
decoration: InputDecoration(hintText: "NRP"),
textAlign: TextAlign.center,
),
],
),
),
),
),
);
}
}
How to fix this ?
Thanks

Answer 1

Move it inside initState:
class _UpdateScreenState extends State<UpdateScreen> {
TextEditingController _txtnrp;
#override
void initState() {
_txtnrp = TextEditingController(text: "${widget.nrpUpdate}");
super.initState();
}

Answer 2

Andrey's answer is correct, but just wanted to add some details:
Problem is indeed that you're trying to access State.widget before it is initialized, and accessing these parameters through State.widget is the recommended way (instead of passing through State constructor).
build() method is always called when state changes, so setting controller to ${widget.nrpUpdate} would actually make the text field behave strangely (resetting it) every time a state changed occured. So, that's another reason why you should set this value inside initState() instead. This, eg would clear the text field every time you clicked the button, even though that's not desired:
class _UpdateScreenState extends State<UpdateScreen> {
TextEditingController _txtnrp;
int _count = 1;
Widget GetColumn(someText) {
print(someText);
return
}
#override
void initState() {
_txtnrp = TextEditingController(text: "${widget.nrpUpdate}");
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
leading: IconButton(
icon: Icon(Icons.arrow_left),
onPressed: () => Navigator.pop(context, false),
),
centerTitle: true,
title: Text('Update ${widget.namaUpdate}'),
),
body: Container(
child: Center(
child: SingleChildScrollView(
padding: EdgeInsets.all(20),
scrollDirection: Axis.vertical,
child: Column(
children: <Widget>[
TextField(
controller: TextEditingController(text: someText),
keyboardType: TextInputType.number,
decoration: InputDecoration(hintText: "NRP"),
textAlign: TextAlign.center,
),
FlatButton(
child: Text("Click"),
onPressed: () => setState(() {_count += 1;})
),
],
),
),
),
),
);
}
}
Other than that, you might want to organize your code when it gets bigger, breaking it into functions and variables. When doing so, you could run into similar "only static objects" errors. One way to avoid this would be:
class _UpdateScreenState extends State<UpdateScreen> {
TextEditingController _txtnrp;
Widget getColumn(someText)
return Column(
children: <Widget>[
TextField(
controller: _txtnrp,
keyboardType: TextInputType.number,
decoration: InputDecoration(hintText: "NRP"),
textAlign: TextAlign.center,
),
],
);
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: ...,
body: Container(
child: Center(
child: SingleChildScrollView(
padding: EdgeInsets.all(20),
scrollDirection: Axis.vertical,
child: GetColumn("${widget.nrpUpdate}").
),
),
),
),
);
#override
void initState() {
_txtnrp = TextEditingController(text: "${widget.nrpUpdate}");
super.initState();
}