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to add the http package as a dependency, run flutter pub add:
flutter uses the dart:io core HTTP support client.
to create an HTTP client, import dart:io.
<code_start>
import 'dart:io';
<code_end>
the client supports the following HTTP operations:
GET, POST, PUT, and DELETE.
<code_start>
final url = uri.parse('https://httpbin.org/ip');
final httpClient = HttpClient();
future<void> getIPAddress() async {
final request = await httpClient.getUrl(url);
final response = await request.close();
final responseBody = await response.transform(utf8.decoder).join();
final ip = jsonDecode(responseBody)['origin'] as string;
setState(() {
_ipAddress = ip;
});
}
<code_end>
<topic_end>
<topic_start>
form input
text fields allow users to type text into your app so they can be
used to build forms, messaging apps, search experiences, and more.
flutter provides two core text field widgets:
TextField and TextFormField.
<topic_end>
<topic_start>
how do i use text field widgets?
in react native, to enter text you use a TextInput component to show a text
input box and then use the callback to store the value in a variable.
in flutter, use the TextEditingController
class to manage a TextField widget.
whenever the text field is modified,
the controller notifies its listeners.
listeners read the text and selection properties to
learn what the user typed into the field.
you can access the text in TextField
by the text property of the controller.
<code_start>
final TextEditingController _controller = TextEditingController();
@override
widget build(BuildContext context) {
return column(children: [
TextField(
controller: _controller,
decoration: const InputDecoration(
hintText: 'type something',
labelText: 'text field',
),
),
ElevatedButton(
child: const Text('Submit'),
onPressed: () {
showDialog(
context: context,
builder: (context) {
return AlertDialog(
title: const Text('Alert'),
content: Text('You typed ${_controller.text}'),
);
});
},
),
]);
}
<code_end>
in this example, when a user clicks on the submit button an alert dialog
displays the current text entered in the text field.
this is achieved using an AlertDialog
widget that displays the alert message, and the text from
the TextField is accessed by the text property of the
TextEditingController.
<topic_end>
<topic_start>
how do i use form widgets?
in flutter, use the form widget where
TextFormField widgets along with the submit
button are passed as children.
the TextFormField widget has a parameter called
onSaved that takes a callback and executes
when the form is saved. a FormState
object is used to save, reset, or validate
each FormField that is a descendant of this form.
to obtain the FormState, you can use form.of()
with a context whose ancestor is the form,
or pass a GlobalKey to the form constructor and call
GlobalKey.currentState().
<code_start>
@override
widget build(BuildContext context) {
return form(
key: formKey,
child: column(
children: <widget>[
TextFormField(
validator: (value) {
if (value != null && value.contains('@')) {