text
stringlengths 1
80
|
|---|
// 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) { |