Why can't long-running computational operations be performed in an asynchronous method?

Long-running computational operations in an asynchronous method executed on the main isolate (UI thread) block the UI. Although the asynchronous method uses Future or async/await, it still runs on the same thread. While a resource-intensive task is running, the UI cannot update, leading to application "freezing".

To perform long operations without blocking the UI, you should use:

• Isolates: Separate execution threads that do not share memory with the main isolate. Communication between isolates is done via ports (SendPort, ReceivePort).
• Compute function: A convenient wrapper for creating and managing isolates for small computations.

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

// Function that performs long computations
int performHeavyComputation(int data) {
  // Simulating long computations
  int result = 0;
  for (int i = 0; i < 1000000000; i++) {
    result += i;
  }
  return result + data;
}

// Using compute to run in another isolate
Future<int> heavyComputationInIsolate(int data) async {
  return compute(performHeavyComputation, data);
}

// Example usage in a StatefulWidget
class MyWidgetState extends State<MyWidget> {
  int computationResult = 0;

  Future<void> _startComputation() async {
    // Call long computations in another isolate
    computationResult = await heavyComputationInIsolate(10);
    setState(() {
      // Update UI after receiving the result
    });
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Text('Computation result: $computationResult'),
          ElevatedButton(
            onPressed: _startComputation,
            child: const Text('Start computation'),
          ),
        ],
      ),
    );
  }
}