this error :
Null check operator used on a null value
happens when we use bang operator (!) on a nullable instance which wasn't initialized.
class Wallet_Page extends StatefulWidget {
@override
State<Wallet_Page> createState() => _Wallet_PageState();
}
class _Wallet_PageState extends State<Wallet_Page> {
TextEditingController _increaseBalance_Cotroller = TextEditingController();
List<TextEditingController> _buyCrypto_Cotroller =
List.generate(100, (i) => TextEditingController());
List<TextEditingController> _sellCrypto_Cotroller =
List.generate(100, (i) => TextEditingController());
getCryptoData data = getCryptoData();
String? _currentUser;
Map? _userData;
String? userName;
String? userLastName;
double? userFiatAsset;
List cryptoName = <String>[];
List cryptoSymbol = <String>[];
List cryptoPrice = <double>[];
List cryptoLogo = <String>[];
List cryptoAsset = <double>[];
int _selectedIndex = 0;
Future<void> getUserData() async {
_currentUser = await FirebaseAuth.instance.currentUser!.email.toString();
print(_currentUser);
await FirebaseFirestore.instance
.collection('users')
.doc(_currentUser)
.get()
.then((value) => {_userData = value.data()});
print(_userData);
if (_userData != null) {
print((_userData ?? {"": ""})['Name']);
print((_userData ?? {"": ""})['LastName']);
print((_userData ?? {"": ""})['FiatAsset']);
//userName = (_userData ?? {"":""})['Name'];
userLastName = (_userData ?? {"":""})['LastName'];
userFiatAsset = (_userData ?? {"":""})['FiatAsset'];
}
}
Future<void> getData() async {
await data.getData();
for (var i = 0; i < data.cryptoName.length; i++) {
cryptoName.insert(i, data.cryptoName[i]);
cryptoSymbol.insert(i, data.cryptoSymbol[i]);
cryptoPrice.insert(i, data.cryptoPrice[i]);
cryptoLogo.insert(i, data.cryptoLogo[i]);
//cryptoAsset.insert(i, 0.0);
// if( _userData![cryptoSymbol[i]] != null){
// cryptoAsset.insert(i, _userData![cryptoSymbol]);
// }else
// {
// cryptoAsset.insert(i, 0);
// }
}
}
@override
initState() {
super.initState();
getUserData().then((value) => setState(() {}));
getData().then((value) => setState(() {}));
//getData();
}
@override
Widget build(BuildContext context) {
return Scaffold(
bottomNavigationBar: Theme(
data: Theme.of(context).copyWith(
canvasColor: Colors.black,
),
child: SizedBox(
height: 50,
child: BottomNavigationBar(
currentIndex: _selectedIndex,
onTap: _onTap,
unselectedItemColor: textColor,
unselectedIconTheme: IconThemeData(color: textColor),
selectedItemColor: Colors.indigo.shade600,
items: [
BottomNavigationBarItem(
icon: Icon(
Icons.logout,
size: 20,
//color: textColor
),
label: "Logout",
),
BottomNavigationBarItem(
icon: Icon(
Icons.currency_bitcoin_sharp,
size: 20,
//color: textColor,
),
label: "Crypto Asset"),
],
),
),
),
backgroundColor: scaffold_color,
body: SafeArea(
child: Center(
child: SingleChildScrollView(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
children: [
Container(
width: MediaQuery.of(context).size.width * 0.9,
height: MediaQuery.of(context).size.height * 0.25,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20),
gradient: LinearGradient(
begin: Alignment.topLeft,
end: Alignment.bottomRight,
stops: [0.2, 0.8],
colors: [Colors.black54, Colors.indigo.shade800]),
),
child: userName != null
? Column(
mainAxisAlignment: MainAxisAlignment.start,
children: [
Text(
"Hi ${userName}! 🧡",
style: GoogleFonts.lato(
textStyle: TextStyle(
color: textColor,
fontSize: 25,
fontWeight: FontWeight.bold,
),
),
),
Text(
" welcome to CryptoWallet! ",
style: GoogleFonts.lato(
textStyle: TextStyle(
color: textColor,
fontSize: 25,
fontWeight: FontWeight.bold,
),
),
),
Padding(
padding: const EdgeInsets.fromLTRB(0, 20, 0, 0),
child: Text(
" Your balance: ",
style: GoogleFonts.lato(
textStyle: TextStyle(
color: textColor,
fontSize: 18,
fontWeight: FontWeight.bold,
),
),
),
),
Center(
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Icon(
Icons.attach_money,
size: 50,
color: Colors.deepOrange,
),
Text(
userFiatAsset!.toStringAsFixed(2),
style: GoogleFonts.lato(
textStyle: TextStyle(
color: textColor,
fontSize: 50,
fontWeight: FontWeight.bold,
),
),
),
Padding(
padding: const EdgeInsets.only(left: 15),
child: CircleAvatar(
radius: 18,
backgroundColor: addButtonColor,
child: IconButton(
onPressed: IncreaseBalance,
icon: Icon(
Icons.add,
color: textColor,
size: 20,
),
),
),
),
],
),
),
],
)
: Center(child: CircularProgressIndicator()),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Container(
width: MediaQuery.of(context).size.width * 0.9,
height: MediaQuery.of(context).size.height * 0.8,
child: cryptoName.length == 100
? ListView.builder(
itemCount: cryptoName.length,
itemBuilder: (BuildContext, index) {
return CryptoCard(
name: cryptoName[index],
logo: cryptoLogo[index],
symbol: cryptoSymbol[index],
price: cryptoPrice[index],
//asset: cryptoAsset[index],
onPressed_sell: () {
onPressed_sell(index);
},
onPressed_buy: () {
//print(index);
onPressed_buy(index);
},
//symbol:cryptoSymbol[index],
);
})
: Center(
child: CircularProgressIndicator(),
)),
),
],
),
),
),
),
);
}
}when I perform this the mentioned error pops up. when I comment the line
userName = _userData!['Name'];
the error is solved, so I understand that the error is from this line.. but my previous prints work well and return the desire value:
print(_userData!['Name']);
so how can this happen? I have a valuable that is not null but the error shows something else.. what is wrong?
