1. final _formKey = GlobalKey<FormState>();
3. @override
4. Widget build(BuildContext context) {
5. return Form(
6. key: _formKey,
7. child: Column(
8. crossAxisAlignment: CrossAxisAlignment.start,
9. children: <Widget>[
10. TextFormField(
11. decoration: const InputDecoration(
12. hintText: 'Enter your email',
13. ),
14. validator: (value) {
15. if (value.isEmpty) {
16. return 'Please enter some text';
17. }
18. return null;
19. },
20. ),
21. Padding(
22. padding: const EdgeInsets.symmetric(vertical: 16.0),
23. child: RaisedButton(
24. onPressed: () {
25. // Validate will return true if the form is valid, or false if
26. // the form is invalid.
27. if (_formKey.currentState.validate()) {
28. // Process data.
29. }
30. },
31. child: Text('Submit'),
32. ),
33. ),
34. ],
35. ),
36. );
37. }

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'),
          ),
        ),
      ],
    ),
  );
}