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// the 'echo' isolate sends its SendPort as the first message.
SendPort sendPort = await receivePort.first;
list msg = await sendReceive(
sendPort,
'https://jsonplaceholder.typicode.com/posts',
);
setState(() {
widgets = msg;
});
}
// the entry point for the isolate.
static future<void> dataLoader(SendPort sendPort) async {
// open the ReceivePort for incoming messages.
ReceivePort port = ReceivePort();
// notify any other isolates what port this isolate listens to.
sendPort.send(port.sendPort);
await for (var msg in port) {
string data = msg[0];
SendPort replyTo = msg[1];
string dataURL = data;
http.Response response = await http.get(Uri.parse(dataURL));
// lots of JSON to parse
replyTo.send(jsonDecode(response.body));
}
}
future sendReceive(SendPort port, msg) {
ReceivePort response = ReceivePort();
port.send([msg, response.sendPort]);
return response.first;
}
<code_end>
here, dataLoader() is the isolate that runs in its own separate
execution thread. in the isolate you can perform more CPU intensive
processing (parsing a big JSON, for example),
or perform computationally intensive math,
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 MaterialApp(
title: 'sample app',
theme: ThemeData(
colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
),
home: const SampleAppPage(),
);
}
}
class SampleAppPage extends StatefulWidget {
const SampleAppPage({super.key});
@override
State<SampleAppPage> createState() => _SampleAppPageState();
}
class _SampleAppPageState extends State<SampleAppPage> {
list widgets = [];
@override
void initState() {
super.initState();
loadData();
}
widget getBody() {
bool showLoadingDialog = widgets.isEmpty;
if (showloadingdialog) {
return getProgressDialog();
} else {
return getListView();
}
}
widget getProgressDialog() {
return const center(child: CircularProgressIndicator());
}
@override
widget build(BuildContext context) {
return scaffold(
appBar: AppBar(
title: const Text('Sample app'),
),
body: getBody(),
);
}
ListView getListView() {
return ListView.builder(
itemCount: widgets.length,
itemBuilder: (context, position) {
return getRow(position);
},
);
}
widget getRow(int i) {