Lernen Isolates for Heavy Computation in Flutter

When building Flutter apps, you want your user interfaces to stay smooth and responsive, even while your app is performing complex or time-consuming work. Dart's single-threaded event loop means that if you run heavy computations directly on the main thread, your UI can stutter, freeze, or become unresponsive. To solve this, Dart provides a feature called isolates, which let you run code in parallel, on a separate thread of execution, without blocking the main thread. Isolates are especially useful in Flutter for offloading CPU-intensive tasks so that your UI remains fluid and interactive.

main.dart


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import 'dart:async';
import 'dart:isolate';

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

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

  print('Doing other work on main thread...');
  int computationResult = await receivePort.first;
  print('Result from isolate: $computationResult');
}

When you use an isolate, you need a way to communicate between the main thread and the isolate. Dart isolates do not share memory, so you send messages using ports. The main thread creates a ReceivePort, which gives you a SendPort to pass into the isolate. The isolate can then send results or updates back to the main thread using this port. This message-passing model allows you to transfer data between isolates efficiently and safely.

main.dart


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import 'dart:isolate';

void computeSquare(List<dynamic> args) {
  int number = args[0];
  SendPort sendPort = args[1];
  int square = number * number;
  sendPort.send(square);
}

void main() async {
  ReceivePort receivePort = ReceivePort();
  await Isolate.spawn(computeSquare, [12, receivePort.sendPort]);
  int result = await receivePort.first;
  print('Square is: $result');
}

Note

Using isolates for heavy computation helps you avoid UI jank and keeps your Flutter apps responsive. Always consider isolates when performing tasks that would otherwise block the main thread, such as complex calculations or data processing.

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main.dart


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import 'dart:async';
import 'dart:isolate';

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

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

  print('Doing other work on main thread...');
  int computationResult = await receivePort.first;
  print('Result from isolate: $computationResult');
}

main.dart


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import 'dart:isolate';

void computeSquare(List<dynamic> args) {
  int number = args[0];
  SendPort sendPort = args[1];
  int square = number * number;
  sendPort.send(square);
}

void main() async {
  ReceivePort receivePort = ReceivePort();
  await Isolate.spawn(computeSquare, [12, receivePort.sendPort]);
  int result = await receivePort.first;
  print('Square is: $result');
}

Note

War alles klar?

Danke für Ihr Feedback!

Abschnitt 2. Kapitel 4