How to Use Isolates for CPU-Intensive Tasks in Dart?

When building Flutter apps, performance is crucial—especially for CPU-heavy operations like image processing, file parsing, or long loops. Dart uses Isolates to run such operations in parallel so your Flutter UI stays smooth and responsive.

In this article, you’ll learn how to use Isolates in Dart, how it compares with the built-in compute() function, and when to choose which.

What Are Isolates in Dart?

Dart’s Isolate is a way to run code in a separate memory and execution context. Unlike traditional threads, Isolates do not share memory. Communication between Isolates is done using message passing via SendPort and ReceivePort.

Use Case: Running a Heavy Calculation in the Background

Let’s say you need to compute a large mathematical result or parse a big JSON file. Doing this on the main thread causes frame drops and app freezing. The solution: run it in an Isolate.

import 'dart:isolate';
import 'package:flutter/material.dart';

void heavyComputation(SendPort sendPort) {
  int result = 0;
  for (int i = 0; i < 100000000; i++) {
    result += i;
  }
  sendPort.send(result);
}

class IsolateExamplePage extends StatefulWidget {
  @override
  _IsolateExamplePageState createState() => _IsolateExamplePageState();
}

class _IsolateExamplePageState extends State<IsolateExamplePage> {
  String _result = 'No result yet';

  Future<void> _runIsolateTask() async {
    final receivePort = ReceivePort();
    await Isolate.spawn(heavyComputation, receivePort.sendPort);

    final result = await receivePort.first;
    setState(() {
      _result = 'Computation result: $result';
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Dart Isolate Example')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(_result),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _runIsolateTask,
              child: Text('Run Heavy Task in Isolate'),
            ),
          ],
        ),
      ),
    );
  }
}

Isolate vs compute() – What’s the Difference?

Frequently Asked Questions (FAQ)

Dart Isolates are powerful tools for improving Flutter app performance when handling heavy operations. For simpler tasks, compute() works well. Choose based on complexity, control, and performance needs.

For more real-world Flutter performance tips, keep reading FlutterFever.com.