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super.dispose();
}
@override
widget build(BuildContext context) {
return scaffold(
appBar: AppBar(title: const Text('Retrieve text input')),
body: padding(
padding: const EdgeInsets.all(16),
child: TextField(controller: myController),
),
floatingActionButton: FloatingActionButton(
// when the user presses the button, show an alert dialog with the
// text the user has typed into our text field.
onPressed: () {
showDialog(
context: context,
builder: (context) {
return AlertDialog(
// retrieve the text the user has typed in using our
// TextEditingController.
content: Text(myController.text),
);
},
);
},
tooltip: 'show me the value!',
child: const Icon(Icons.text_fields),
),
);
}
}
<code_end>
you can find more information and the full code listing in
retrieve the value of a text field,
from the flutter cookbook.
<topic_end>
<topic_start>
placeholder in a text field
in flutter, you can easily show a “hint” or a placeholder text
for your field by adding an InputDecoration object
to the decoration constructor parameter for the text widget:
<code_start>
center(
child: TextField(
decoration: InputDecoration(hintText: 'this is a hint'),
),
)
<code_end>
<topic_end>
<topic_start>
showing validation errors
just as you would with a “hint”, pass an InputDecoration object
to the decoration constructor for the text widget.
however, you don’t want to start off by showing an error.
instead, when the user has entered invalid data,
update the state, and pass a new InputDecoration object.
<code_start>
import 'package:flutter/material.dart';
void main() {
runApp(const SampleApp());
}
class SampleApp extends StatelessWidget {
const SampleApp({super.key});
// this widget is the root of your application.
@override
widget build(BuildContext context) {
return const MaterialApp(
title: 'sample app',
home: SampleAppPage(),
);
}
}
class SampleAppPage extends StatefulWidget {
const SampleAppPage({super.key});
@override
State<SampleAppPage> createState() => _SampleAppPageState();
}
class _SampleAppPageState extends State<SampleAppPage> {
string? _errorText;
bool isEmail(String em) {
string emailRegexp =
r'^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|'
r'(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|'
r'(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$';
RegExp regExp = RegExp(emailRegexp);
return regExp.hasMatch(em);
}
@override
widget build(BuildContext context) {
return scaffold(
appBar: AppBar(
title: const Text('Sample app'),
),
body: center(
child: TextField(
onSubmitted: (text) {
setState(() {
if (!isemail(text)) {
_errorText = 'error: this is not an email';
} else {