Whenever I click on any textfield of the form, I get the following error in the screen:
Null check operator used on a null value See also https://flutter.dev/docs
Also, the console is showing the following error: The following ArgumentError was thrown resolving an image codec: Invalid argument(s): No host specified in URI file:///
Here is the code of the login form. I can't figure out why this error is showing up.
// .....
child: Form(
key: _formKey,
autovalidateMode: AutovalidateMode.disabled,
child: ListView.builder(
itemCount: 1,
shrinkWrap: false,
itemBuilder: (BuildContext context, int index) {
return Column(
children: [
SizedBox(height: 30),
HeroImage(),
SizedBox(height: 20),
Container(
child: Padding(
padding: const EdgeInsets.only(left: 20, right: 20),
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: [
AppLableWidget(
title: Languages.of(context)!.labelEmail,
),
CardTextFieldWidget(
focus: (v) {
FocusScope.of(context).nextFocus();
},
textInputAction: TextInputAction.next,
hintText: Languages.of(context)!.labelEnterYourEmailID,
textInputType: TextInputType.emailAddress,
textEditingController: _textEmail,
validator: kvalidateEmail,
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
AppLableWidget(
title: Languages.of(context)!.labelPassword,
),
],
),
CardPasswordTextFieldWidget(
textEditingController: _textPassword,
validator: kvalidatePassword,
hintText: Languages.of(context)!.labelEnterYourPassword,
isPasswordVisible: _passwordVisible),
Row(
mainAxisAlignment: MainAxisAlignment.end,
crossAxisAlignment: CrossAxisAlignment.end,
children: [
/* Row(
children: [
Padding(
padding: const EdgeInsets.all(10.0),
child: ClipRRect(
clipBehavior: Clip.hardEdge,
borderRadius: BorderRadius.all(Radius.circular(5)),
child: SizedBox(
width: 40.0,
height: ScreenUtil().setHeight(40),
child: Card(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10.0),
),
child: Container(
child: Theme(
data: ThemeData(
unselectedWidgetColor: Colors.transparent,
),
child: Checkbox(
value: isRememberMe,
onChanged: (state) =>
setState(() => isRememberMe = !isRememberMe),
activeColor: Colors.transparent,
checkColor: Color(Constants.colorTheme),
materialTapTargetSize: MaterialTapTargetSize.padded,
),
),
),
),
),
),
),
Text(
Languages.of(context)!.labelRememberMe,
style: TextStyle(fontSize: 14.0, fontFamily: Constants.appFont),
),
],
),*/
Container(
padding: const EdgeInsets.all(10.0),
alignment: Alignment.centerRight,
child: GestureDetector(
onTap: () {
Navigator.of(context).push(Transitions(
transitionType: TransitionType.fade,
curve: Curves.bounceInOut,
reverseCurve: Curves.fastLinearToSlowEaseIn,
widget: ChangePassword()));
},
child: Text(
Languages.of(context)!.labelForgotPassword,
style: TextStyle(fontFamily: Constants.appFontBold,fontSize: ScreenUtil().setSp(16),),
),
),
),
],
),
Padding(
padding: EdgeInsets.only(left: 20.0, right: 20,top: 10, bottom: 10),
child: RoundedCornerAppButton(
onPressed: () {
if (
_formKey.currentState!.validate()) {
// if (SharedPreferenceUtil.getString(
// Constants
// .appPush_oneSingleToken)
// .isEmpty) {
// getOneSingleToken(SharedPreferenceUtil
// .getString(Constants
// .appSettingCustomerAppId));
// } else {
// }
Constants.checkNetwork().whenComplete(() => callUserLogin());
} else {
setState(() {
// validation error
//_autoValidate = true;
});
}
},
btnLabel: Languages.of(context)!.labelLogin,
),
),
SizedBox(
height: 10.0,
),
GestureDetector(
onTap: () {
Navigator.of(context).push(Transitions(
transitionType: TransitionType.slideUp,
curve: Curves.bounceInOut,
reverseCurve: Curves.fastLinearToSlowEaseIn,
widget: CreateNewAccount()));
},
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text(
Languages.of(context)!.labelDonthaveAcc,
style: TextStyle(fontFamily: Constants.appFont,fontSize: ScreenUtil().setSp(14),),
),
Text(
Languages.of(context)!.labelCreateNow,
style: TextStyle(fontFamily: Constants.appFontBold,fontSize: ScreenUtil().setSp(16),),
),
],
),
),
SizedBox(
height: 20,
),
InkWell(
onTap: () {
Navigator.of(context).push(Transitions(
transitionType: TransitionType.slideUp,
curve: Curves.bounceInOut,
reverseCurve: Curves.fastLinearToSlowEaseIn,
widget: DashboardScreen(0)));
},
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text(
Languages.of(context)!.labelSkipNow,
style: TextStyle(
color: Colors.black,
decoration: TextDecoration.underline,
decorationColor: Colors.black,
fontWeight: FontWeight.bold,
decorationThickness: 5,
fontSize: ScreenUtil().setSp(16),
fontFamily: Constants.appFontBold,),
),
],
),
),
],
),
),
),
],
);
},
),
),
//.....
String kvalidatePassword(String? value) {
Pattern pattern = r'^(?=.*?[a-z])(?=.*?[0-9]).{8,}$';
if (value!.isEmpty) return 'Username is Required.';
final RegExp nameExp = new RegExp(pattern as String);
if (!nameExp.hasMatch(value))
return 'Please enter only alphabetical characters.';
return value;
}
String kvalidatePassword(String? value) {
Pattern pattern = r'^(?=.*?[a-z])(?=.*?[0-9]).{8,}$';
if (value!.isEmpty) return 'Username is Required.';
final RegExp nameExp = new RegExp(pattern as String);
if (!nameExp.hasMatch(value))
return 'Please enter only alphabetical characters.';
return value;
}
Please help. New to Flutter and this is an old project I need to fix.
CodePudding user response：
AppLableWidget(title: Languages.of(context)!.labelEmail),
Try This...
AppLableWidget(title: Languages.of(context)?.labelEmail ?? ''),
String value = 'Test String';
String? value1;
Text(value ?? ''), // output --> Test String
Text(value1 ?? ''), // output --> ''
// here manage if value are null then return ''(Blank Text) otherwise Text.
CodePudding user response：
This error occurs when you use a bang operator (!) on a nullable instance which wasn't initialized.
For example:
String? foo; // Nullable String
void main() {
var len = foo!.length; // Runtime error: Null check operator used on a null value
}
Solution:
You need to find out where you're using the bang operator in your code. Once you are there, you can use any of the following solutions:
Use a local variable
var f = foo;
if (f != null) {
var len = f.length; // Safe
}
Use ?. and ??
var len = foo?.length ?? 0; // Provide a default value if foo was null.