NoSuchMethodError: The method 'validate' was called on null

user_10379808 0
Viewed 16879

Im a beginer in Flutter and here is the problem- im trying to build a form with validation and 'Submit' button which must navigate to a new screen but there is 'NoSuchMethodError: The method 'validate' was called on null' in debuger when i press this button . Here is the code: 

class _SignInPage extends State<SignInPage> {
  final scaffoldKey = GlobalKey<ScaffoldState>();
  final formKey = GlobalKey<FormState>();

  String _email;
  String _password;

  void _submit() {
    final form = formKey.currentState;

    if (form.validate()) {
      form.save();
      _performLogin();
    }
  }

  void _performLogin() {
    Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => ConnectPage()),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: scaffoldKey,
      body: new Container(
          margin: new EdgeInsets.symmetric(vertical: 200.0, horizontal: 35.0),
          padding: EdgeInsets.all(20.0),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            key: formKey,
            children: [
              TextFormField(
                keyboardType: TextInputType.emailAddress,
                autofocus: false,
                decoration: InputDecoration(
                    contentPadding: EdgeInsets.fromLTRB(20.0, 10.0, 20.0, 10.0),
                    border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(20.0)),
                    labelText: 'Email'),
                validator: (val) =>
                    !val.contains('@') ? 'Not a valid email.' : null,
                onSaved: (val) => _email = val,
              ),
              TextFormField(
                autofocus: false,
                obscureText: true,
                decoration: InputDecoration(
                    hintText: 'Password',
                    contentPadding: EdgeInsets.fromLTRB(20.0, 10.0, 20.0, 10.0),
                    border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(20.0)),
                    labelText: 'Password'),
                validator: (val) =>
                    val.length < 6 ? 'Password too short.' : null,
                onSaved: (val) => _password = val,
              ),
              Row(mainAxisAlignment: MainAxisAlignment.spaceBetween, children: [
                new Row(children: [
                  FlatButton(
                    child:
                        Text('Sign Up', style: TextStyle(color: Colors.black)),
                    onPressed: () {
                      Navigator.push(
                        context,
                        MaterialPageRoute(builder: (context) => SignUpPage()),
                      );
                    },
                  ),
                  FlatButton(
                    child:
                        Text('Sign In', style: TextStyle(color: Colors.black)),
                    onPressed: () {
                      // Navigate to second screen when tapped!
                    },
                  ),
                ]),
                new Row(children: [
                  Radio(
                    activeColor: Colors.blue,
                    value: Colors.grey,
                    onChanged: (activeColor) {},
                  ),
                  Text(
                    "Keep me signed in",
                    style: new TextStyle(color: Colors.black),
                  )
                ])
              ]),
              RaisedButton(
                color: Colors.blue,
                onPressed: _submit,
                child: new Text('Sign in'),
              ),
            ],
          )),
    );
  }
}
  1. How can i fix that?
  2. How to add space between two forms?
dart flutter android
7 Answers

You have to wrap your TextFormFields with the Form widget.

As per docs,

Each individual form field should be wrapped in a FormField widget, with the Form widget as a common ancestor of all of those*.

user_53059620

This error occures when:

  1. Form contains only one TextFormField
  2. You didn't bind key to Form
  3. Some widgets in your Form are not wrapped with FormField widget
user_87735600

In my case i forgot the key parameter of Form.

user_9567010

Try to wrap your TextFieldField in Form widget and also put key parameter. You might want to check out TextField and errorText property.

user_107587100

You may miss: 

final _formKey = GlobalKey<FormState>(); 

key: _formKey,

    final _formKey = GlobalKey<FormState>();

    @override
    Widget build(BuildContext context) {
      return Form(
        key: _formKey,
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            TextFormField(
              decoration: const InputDecoration(
                hintText: 'Enter your email',
              ),
              validator: (value) {
                if (value.isEmpty) {
                  return 'Please enter some text';
                }
                return null;
              },
            ),
            Padding(
              padding: const EdgeInsets.symmetric(vertical: 16.0),
              child: RaisedButton(
                onPressed: () {
                  // Validate will return true if the form is valid, or false if
                  // the form is invalid.
                  if (_formKey.currentState.validate()) {
                    // Process data.
                  }
                },
                child: Text('Submit'),
              ),
            ),
          ],
        ),
      );
    }
user_108341970

Try to wrap your TextFieldField in Form widget and also put key parameter.

final _formKey = GlobalKey<FormState>();

Example code:

  Form(
    key: _formKey,
    child: TextFormField(
          decoration: const InputDecoration(
            hintText: 'Enter your email',
          ),
          validator: (value) {
            if (value.isEmpty) {
              return 'Please enter some text';
            }
            return null;
          },
        ),
     ),

Note: In is case, please ensure key value

user_127559550

In my case you forgot the key parameter of Form.

final _formKey = GlobalKey<FormState>();
Form(
 key: _formKey,);
user_97997530
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