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<topic_end>
<topic_start>
How do I retrieve user input?
Xamarin.Forms elements allow you to directly query the element
to determine the state of its properties,
or whether it’s bound to a property in a ViewModel.Retrieving information in Flutter is handled by specialized widgets
and is different from how you are used to.
If you have a TextFieldor a TextFormField,
you can supply a TextEditingController
to retrieve user input:
<code_start>import 'package:flutter/material.dart';
class MyForm extends StatefulWidget {
const MyForm({super.key});
@override
State<MyForm> createState() => _MyFormState();
}
class _MyFormState extends State<MyForm> {
/// Create a text controller and use it to retrieve the current value
/// of the TextField.
final TextEditingController myController = TextEditingController();
@override
void dispose() {
// Clean up the controller when disposing of the widget.
myController.dispose();
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 that the user has typed into our text field.
onPressed: () {
showDialog(
context: context,
builder: (context) {
return AlertDialog(
// Retrieve the text that the user has entered using the
// 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>
What is the equivalent of a Placeholder on an Entry?
In Xamarin.Forms, some Elements support a Placeholder property
that you can assign a value to. For example:In Flutter, you can easily show a “hint” or a placeholder text
for your input by adding an InputDecoration object
to the decoration constructor parameter for the text widget.
<code_start>TextField(
decoration: InputDecoration(hintText: 'This is a hint'),
),<code_end>
<topic_end>
<topic_start>
How do I show validation errors?
With Xamarin.Forms, if you wished to provide a visual hint of a
validation error, you would need to create new properties and
VisualElements surrounding the Elements that had validation errors.In Flutter, you pass through 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 {
/// This widget is the root of your application.
const SampleApp({super.key});
@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;
String? _getErrorText() {
return _errorText;