问题
The following NoSuchMethodError was thrown while handling a gesture: The method 'save' was called on null. Receiver: null Tried calling: save()
I'm creating a page to update user registration data, and when I click on update this error appears and nothing happens. I'm learning flutter now, and there's a lot that I don't know, can someone help me?
import 'package:flutter/material.dart';
import '../../generated/l10n.dart';
import '../models/user.dart';
import '../helpers/helper.dart';
import '../elements/BlockButtonWidget.dart';
import '../helpers/app_config.dart' as config;
import 'package:mvc_pattern/mvc_pattern.dart';
import '../repository/user_repository.dart' as repository;
import '../repository/user_repository.dart';
class SettingsController extends ControllerMVC {
GlobalKey<FormState> loginFormKey;
GlobalKey<ScaffoldState> scaffoldKey;
SettingsController() {
loginFormKey = new GlobalKey<FormState>();
this.scaffoldKey = new GlobalKey<ScaffoldState>();
}
void update(User user) async {
user.deviceToken = null;
repository.update(user).then((value) {
scaffoldKey?.currentState?.showSnackBar(SnackBar(
content: Text("Atualizado com Sucesso"),
));
});
}
}
class ProfileSettingsDialog extends StatefulWidget {
final User user;
final VoidCallback onChanged;
ProfileSettingsDialog({Key key, this.user, this.onChanged}) : super(key: key);
@override
_ProfileSettingsDialogState createState() => _ProfileSettingsDialogState();
}
class _ProfileSettingsDialogState extends State<ProfileSettingsDialog> {
GlobalKey<FormState> _profileSettingsFormKey = new GlobalKey<FormState>();
@override
Widget build(BuildContext context) {
return WillPopScope(
onWillPop: Helper.of(context).onWillPop,
child: Scaffold(
resizeToAvoidBottomPadding: false,
body: Stack(
alignment: AlignmentDirectional.topCenter,
children: <Widget>[
Positioned(
top: 0,
child: Container(
width: config.App(context).appWidth(100),
height: config.App(context).appHeight(29.5),
decoration: BoxDecoration(color: Theme.of(context).accentColor),
),
),
Positioned(
top: config.App(context).appHeight(29.5) - 120,
child: Container(
width: config.App(context).appWidth(84),
height: config.App(context).appHeight(29.5),
child: Text(
S.of(context).lets_start_with_register,
style: Theme.of(context).textTheme.headline2.merge(TextStyle(color: Theme.of(context).primaryColor)),
),
),
),
Positioned(
top: config.App(context).appHeight(29.5) - 50,
child: Container(
decoration: BoxDecoration(color: Theme.of(context).primaryColor, borderRadius: BorderRadius.all(Radius.circular(10)), boxShadow: [
BoxShadow(
blurRadius: 50,
color: Theme.of(context).hintColor.withOpacity(0.2),
)
]),
margin: EdgeInsets.symmetric(
horizontal: 20,
),
padding: EdgeInsets.symmetric(vertical: 50, horizontal: 27),
width: config.App(context).appWidth(88),
// height: config.App(context).appHeight(55),
child: Form(
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
TextFormField(
keyboardType: TextInputType.text,
onSaved: (input) => widget.user.phone = input,
validator: (input) => input.trim().length < 3 ? S.of(context).not_a_valid_phone : null,
decoration: InputDecoration(
labelText: "Celular",
labelStyle: TextStyle(color: Theme.of(context).accentColor),
contentPadding: EdgeInsets.all(12),
hintText: S.of(context).john_doe,
hintStyle: TextStyle(color: Theme.of(context).focusColor.withOpacity(0.7)),
prefixIcon: Icon(Icons.person_outline, color: Theme.of(context).accentColor),
border: OutlineInputBorder(borderSide: BorderSide(color: Theme.of(context).focusColor.withOpacity(0.2))),
focusedBorder: OutlineInputBorder(borderSide: BorderSide(color: Theme.of(context).focusColor.withOpacity(0.5))),
enabledBorder: OutlineInputBorder(borderSide: BorderSide(color: Theme.of(context).focusColor.withOpacity(0.2))),
),
),
SizedBox(height: 30),
TextFormField(
keyboardType: TextInputType.text,
onSaved: (input) => widget.user.address = input,
validator: (input) => input.trim().length < 3 ? S.of(context).not_a_valid_address : null,
decoration: InputDecoration(
labelText: "Endereço",
labelStyle: TextStyle(color: Theme.of(context).accentColor),
contentPadding: EdgeInsets.all(12),
hintText: 'johndoe@gmail.com',
hintStyle: TextStyle(color: Theme.of(context).focusColor.withOpacity(0.7)),
prefixIcon: Icon(Icons.alternate_email, color: Theme.of(context).accentColor),
border: OutlineInputBorder(borderSide: BorderSide(color: Theme.of(context).focusColor.withOpacity(0.2))),
focusedBorder: OutlineInputBorder(borderSide: BorderSide(color: Theme.of(context).focusColor.withOpacity(0.5))),
enabledBorder: OutlineInputBorder(borderSide: BorderSide(color: Theme.of(context).focusColor.withOpacity(0.2))),
),
),
SizedBox(height: 30),
TextFormField(
keyboardType: TextInputType.text,
onSaved: (input) => widget.user.bio = input,
validator: (input) => input.trim().length < 3 ? S.of(context).not_a_valid_biography : null,
decoration: InputDecoration(
labelText: "Biografia",
labelStyle: TextStyle(color: Theme.of(context).accentColor),
contentPadding: EdgeInsets.all(12),
hintText: 'johndoe@gmail.com',
hintStyle: TextStyle(color: Theme.of(context).focusColor.withOpacity(0.7)),
prefixIcon: Icon(Icons.alternate_email, color: Theme.of(context).accentColor),
border: OutlineInputBorder(borderSide: BorderSide(color: Theme.of(context).focusColor.withOpacity(0.2))),
focusedBorder: OutlineInputBorder(borderSide: BorderSide(color: Theme.of(context).focusColor.withOpacity(0.5))),
enabledBorder: OutlineInputBorder(borderSide: BorderSide(color: Theme.of(context).focusColor.withOpacity(0.2))),
),
),
SizedBox(height: 30),
BlockButtonWidget(
text: Text(
S.of(context).register,
style: TextStyle(color: Theme.of(context).primaryColor),
),
color: Theme.of(context).accentColor,
onPressed: () {
_profileSettingsFormKey.currentState.save();
widget.onChanged();
Navigator.pop(context);
update(currentUser.value);
//setState(() {});
},
// widget.update(currentUser.value);
),
SizedBox(height: 25),
// FlatButton(
// onPressed: () {
// Navigator.of(context).pushNamed('/MobileVerification');
// },
// padding: EdgeInsets.symmetric(vertical: 14),
// color: Theme.of(context).accentColor.withOpacity(0.1),
// shape: StadiumBorder(),
// child: Text(
// 'Register with Google',
// textAlign: TextAlign.start,
// style: TextStyle(
// color: Theme.of(context).accentColor,
// ),
// ),
// ),
],
),
),
),
),
],
),
),
);
}
InputDecoration getInputDecoration({String hintText, String labelText}) {
return new InputDecoration(
hintText: hintText,
labelText: labelText,
hintStyle: Theme.of(context).textTheme.bodyText2.merge(
TextStyle(color: Theme.of(context).focusColor),
),
enabledBorder: UnderlineInputBorder(borderSide: BorderSide(color: Theme.of(context).hintColor.withOpacity(0.2))),
focusedBorder: UnderlineInputBorder(borderSide: BorderSide(color: Theme.of(context).hintColor)),
floatingLabelBehavior: FloatingLabelBehavior.auto,
labelStyle: Theme.of(context).textTheme.bodyText2.merge(
TextStyle(color: Theme.of(context).hintColor),
),
);
}
}
回答1:
You should bind the key _profileSettingsFormKey to Form, else the key would not get any state and so the currentState would be null
thus calling save() on null throws the exception
Form(
key: _profileSettingsFormKey,
child: ...
)
回答2:
_profileSettingsFormKey is null, you need to use a Form widget and bind the key to it:
return Form(
key: _profileSettingsFormKey,
回答3:
You forgot to assign the key to your Form, so the currentState of the key is null.
Form(
key: _profileSettingsFormKey,
// ...
)
回答4:
thank you, now this error is showing
The setter 'address=' was called on null. Receiver: null Tried calling: address="siahduiasudi, 189"
来源：https://stackoverflow.com/questions/62775552/i-flutter-8686-another-exception-was-thrown-nosuchmethoderror-the-method