Flutter数据流隔离插件stream_isolate的使用

Flutter数据流隔离插件stream_isolate的使用

API Reference

• Dart Docs

基本使用

要使用StreamIsolate，可以调用StreamIsolate.spawn，并传入与Isolate.spawn相同的参数。然后可以使用返回的实例订阅由子线程发布的的事件。

final streamIsolate = await StreamIsolate.spawn(doWork);
await for (final i in streamIsolate.stream) {
  print(i);
}

Stream<int> doWork() async* {
  yield 1;
  yield 2;
  yield 3;
  yield 4;
  yield 5;
}

双向通信

也可以调用BidirectionalStreamIsolate.spawn（或StreamIsolate.spawnBidirectional）来创建一个暴露额外通信流以发送消息到实例的子线程：

final streamIsolate = await BidirectionalStreamIsolate.spawn(doWork);
await for (final i in streamIsolate.stream) {
  print(i);
  streamIsolate.send('received');
}

Stream<int> doWorkWithListener(Stream<String> inc) async* {
  inc.listen((msg) => print('from main: $msg'));

  yield 1;
  yield 2;
  yield 3;
  yield 4;
  yield 5;
}

传递初始参数

可以可选地发送一个参数，在子线程首次运行时将其传递给函数。这通过StreamIsolate.spawnWithArgument和BidirectionalStreamIsolate.spawnWithArgument方法实现。

class IsolateArgs {
  final int index;
  final String name;

  const IsolateArgs(this.index, this.name);
}

...

final args = IsolateArgs(1, 'Worker Isolate 1');
final streamIsolate = await StreamIsolate.spawnWithArgument(doWork, argument: args);
await for (final i in streamIsolate.stream) {
  print(i);
  streamIsolate.send('received');
}

Stream<int> doWorkWithListener(Stream<String> inc, IsolateArgs args) async* {
  print('Starting worker isolate ${args.name}, Index: ${args.index}');

  yield 1;
  yield 2;
  yield 3;
  yield 4;
  yield 5;
}

示例

• Vanilla - 一个简单的使用流隔离的示例。
• RxDart - 使用RxDart管理隔离流的一个示例。
• Multithreaded Noise - 一个使用流隔离的Flutter应用，用于生成动画Perlin Noise。

示例代码

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Stream Isolate Example')),
        body: StreamIsolateExample(),
      ),
    );
  }
}

class StreamIsolateExample extends StatefulWidget {
  [@override](/user/override)
  _StreamIsolateExampleState createState() => _StreamIsolateExampleState();
}

class _StreamIsolateExampleState extends State<StreamIsolateExample> {
  final Stream<int> _isolateStream = Stream<int>.empty();

  void _startIsolate() async {
    try {
      final isolate = await StreamIsolate.spawn(() {
        var count = 0;
        while (true) {
          setState(() {
            _isolateStream.add(count++);
          });
        }
      });

      // 订阅子线程发布的内容
      isolate.stream.listen((value) {
        print('Received from isolate: $value');
      });
    } catch (e) {
      print('Error starting isolate: $e');
    }
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Center(
      child: ElevatedButton(
        onPressed: _startIsolate,
        child: Text('Start Isolate'),
      ),
    );
  }
}