isolate_runner_mixin

A Flutter-aware Dart mixin for easily running CPU-intensive tasks, including those that use Flutter plugins, in a background isolate.

Why use this package?

Flutter applications run on a single thread, the UI thread. If you perform long-running or computationally intensive tasks directly on this thread, your UI can become unresponsive, leading to "jank" and a poor user experience. Dart's Isolates provide a way to run code concurrently in separate memory spaces, preventing UI blocking.

However, using raw dart:isolate APIs can be verbose, especially when dealing with Flutter plugins, which require specific initialization (BackgroundIsolateBinaryMessenger.ensureInitialized) within the background isolate.

This package provides a simple IsolateRunnerMixin that encapsulates this boilerplate, allowing you to easily offload any FutureOr<T> Function() to a background isolate.

Key Features

Simple API: A single runInIsolate method.

Flutter Plugin Compatible: Automatically initializes BackgroundIsolateBinaryMessenger in the background isolate using the RootIsolateToken.

UI Thread Protection: Ensures heavy computations run off the main thread.

Graceful Fallback: Automatically runs tasks on the current thread if no Flutter binding is available (e.g., in pure Dart tests).

Unique Mixin Design: Integrates isolate functionality directly into your classes, providing a clean, object-oriented API that feels more natural than using top-level functions or helper classes.

Installation

Add this to your pubspec.yaml file:

dependencies

  isolate_runner_mixin: <latest>

Then, run flutter pub get.

Usage

Apply the Mixin

Apply IsolateRunnerMixin to any class where you want to run tasks in a background isolate.

import 'package:isolate_runner_mixin/isolate_runner_mixin.dart';
import 'package:fast_rsa/fast_rsa.dart'; // Example plugin usage

class MyService with IsolateRunnerMixin {
  // Your service logic
  String _publicKey = '...'; // Example data

  Future<bool> verifyData(String data, String signature) async {
    // Use runInIsolate to offload the heavy work
    return await runInIsolate(() async {
      // This code runs in the background isolate
      await Future.delayed(const Duration(milliseconds: 100)); // Simulate work
      final isValid = await RSA.verifyPKCS1v15(signature, data, Hash.SHA256, _publicKey);
      return isValid;
    });
  }
}

While Isolate.run can implicitly capture variables from closures, it's generally safer and more explicit to pass all necessary data to a top-level or static function that performs the heavy work. This function will then be called from within the runInIsolate's closure.

// This must be a top-level function or a static method.
// It receives all its data via explicit arguments.
import 'package:fast_rsa/fast_rsa.dart';

Future<bool> _performVerification(String data, String signature, String publicKey) async {
  // This code runs in the background isolate
  await Future.delayed(const Duration(milliseconds: 100)); // Simulate work
  final isValid = await RSA.verifyPKCS1v15(signature, data, Hash.SHA256, publicKey);
  return isValid;
}

class MyService with IsolateRunnerMixin {
  String _publicKey = '...'; // Example data

  Future<bool> verifyData(String data, String signature) async {
    return await runInIsolate(() async {
      // Call the top-level function with explicit arguments
      return await _performVerification(data, signature,_publicKey);
    });
  }
}

Example App

For a complete example, see the example/ directory in the package repository. The example demonstrates using the mixin to run both a CPU-intensive loop and a plugin-like task while keeping the UI responsive.

Contributing

Feel free to open issues or pull requests on GitHub.

License

This package is licensed under the MIT License. See the LICENSE file for details.

Libraries

isolate_runner_mixin