text
stringlengths
1
474
such as encryption or signal processing.You can run the full example below:
<code_start>import 'dart:async';
import 'dart:convert';
import 'dart:isolate';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
void main() {
runApp(const SampleApp());
}
class SampleApp extends StatelessWidget {
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> {
List<Map<String, dynamic>> data = <Map<String, dynamic>>[];
@override
void initState() {
super.initState();
loadData();
}
bool get showLoadingDialog => data.isEmpty;
Future<void> loadData() async {
final ReceivePort receivePort = ReceivePort();
await Isolate.spawn(dataLoader, receivePort.sendPort);
// The 'echo' isolate sends its SendPort as the first message
final SendPort sendPort = await receivePort.first as SendPort;
final List<Map<String, dynamic>> msg = await sendReceive(
sendPort,
'https://jsonplaceholder.typicode.com/posts',
);
setState(() {
data = msg;
});
}
// The entry point for the isolate
static Future<void> dataLoader(SendPort sendPort) async {
// Open the ReceivePort for incoming messages.
final ReceivePort port = ReceivePort();
// Notify any other isolates what port this isolate listens to.
sendPort.send(port.sendPort);
await for (final dynamic msg in port) {
final String url = msg[0] as String;
final SendPort replyTo = msg[1] as SendPort;
final Uri dataURL = Uri.parse(url);
final http.Response response = await http.get(dataURL);
// Lots of JSON to parse
replyTo.send(jsonDecode(response.body) as List<Map<String, dynamic>>);
}
}
Future<List<Map<String, dynamic>>> sendReceive(SendPort port, String msg) {
final ReceivePort response = ReceivePort();
port.send(<dynamic>[msg, response.sendPort]);
return response.first as Future<List<Map<String, dynamic>>>;
}
Widget getBody() {
if (showLoadingDialog) {
return getProgressDialog();
}
return getListView();
}
Widget getProgressDialog() {
return const Center(child: CircularProgressIndicator());
}
ListView getListView() {
return ListView.builder(
itemCount: data.length,
itemBuilder: (context, index) {
return getRow(index);
},
);
}
Widget getRow(int index) {
return Padding(
padding: const EdgeInsets.all(10),
child: Text('Row ${data[index]['title']}'),
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('Sample App')),
body: getBody(),
);
}
}<code_end>
<topic_end>
<topic_start>
How do I make network requests?
In Xamarin.Forms you would use HttpClient.