Field 'urlVar' has not been initialized. error in Flutter - flutter

Question

I have a settings page. On this page I configure "Url". I write it down and save it. Everything is simple. But I want to make sure that the next time I visit this page I have already seen the saved Url. I download it through the shared_preferences package (where I saved it). But there was an initialization error. Someone can help me with this. So that after opening the page I saw the saved Url and could edit it.
My code
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:test/setting/сonfiguration_styles.dart';
class Setting extends StatefulWidget {
#override
_EditSettingPageState createState() => _EditSettingPageState();
}
class _EditSettingPageState extends State<Setting> {
late String urlVar;
late TextEditingController _apiController = TextEditingController();
_loadvariable() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
setState(() {
urlVar = (prefs.getString('apiUrl'))?? "";
});
}
#override
void initState() {
_loadvariable()?? "";
_apiController = TextEditingController( text: urlVar )
..addListener(() {
setState(() {});
});
super.initState();
}
#override
void dispose() {
_apiController.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
child: GestureDetector(
onTap: () {
FocusScope.of(context).unfocus();
},
child: ListView(
children: [
TextFormField(
controller: _apiController,
cursorColor: StyleSettingPage.cursorColor,
style: StyleSettingPage.textBody,
),
SizedBox(height: StyleSettingPage.heightBtwButtItem),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
RaisedButton(
onPressed: seveSettingUrl,
child: Text(
"Save",
style: StyleSettingPage.textButton
),
)
],
)
],
),
),
),
);
}
Future<void> seveSettingUrl() async {
SharedPreferences prefs = await SharedPreferences
.getInstance();
prefs.setString('apiUrl', _apiController.text);
}
}

Answer 1

Check this out:
First Page
import 'package:debounce/my_new_page.dart';
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
class WritePage extends StatefulWidget {
const WritePage({Key? key}) : super(key: key);
#override
State<WritePage> createState() => _WritePageState();
}
class _WritePageState extends State<WritePage> {
final TextEditingController controller = TextEditingController();
#override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
child: GestureDetector(
onTap: () {
FocusScope.of(context).unfocus();
},
child: ListView(
children: [
TextFormField(
controller: controller,
),
SizedBox(height: 100),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
RaisedButton(
onPressed: ()async{
SharedPreferences prefs = await SharedPreferences
.getInstance();
prefs.setString('apiUrl', controller.text);
Navigator.push(
context,
MaterialPageRoute(builder: (context) => Edit()),
);
},
child: Text(
"Save",
),
)
],
)
],
),
),
),
);
}
}
Second Page
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
class Edit extends StatefulWidget {
#override
_EditSettingPageState createState() => _EditSettingPageState();
}
class _EditSettingPageState extends State<Edit> {
var urlVar;
late TextEditingController _apiController = TextEditingController();
_loadvariable() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
setState(() {
urlVar = (prefs.getString('apiUrl'))?? "";
print("Get URL VALUE: $urlVar");
});
}
#override
void initState() {
_loadvariable();
super.initState();
}
#override
void dispose() {
_apiController.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
return SafeArea(
child: Scaffold(
body: Container(
child: GestureDetector(
onTap: () {
FocusScope.of(context).unfocus();
},
child: Column(
children: [TextFormField(
controller: TextEditingController( text: urlVar ),
decoration: InputDecoration(
// hintStyle: TextStyle(
// color: Colors.purple,
// fontStyle: FontStyle.italic,
// ),
),
),
SizedBox(height: 100),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
RaisedButton(
onPressed: ()async{
SharedPreferences prefs = await SharedPreferences
.getInstance();
prefs.setString('apiUrl', _apiController.text);
print("SET URL VALUE: $urlVar");
},
child: Text(
"Edit",
),
)
],
)],
)
),
),
),
);
}
}