未处理的异常：无效参数：隔离消息中的非法参数：（对象扩展 NativeWrapper - 库：'dart：ui' 类：路径）

Question

谁能告诉我这段代码有什么问题吗？

void onPressed() async {
    //Navigator.pushNamed(context, "/screen2", arguments: []);
    var receivePort = ReceivePort();
    await Isolate.spawn(gotoNext, [receivePort.sendPort]);
    final msg = await receivePort.first;
    print(msg);
  }

  void gotoNext(List<dynamic> args) {
    SendPort sendPort = args[0];
    log(args.toString());
    Isolate.exit(sendPort, "OK");
  }

E / flutter（12062）：[错误：flutter/lib/ui/ui_dart_state.cc（209）]未处理的异常：无效参数：隔离消息中的非法参数：（对象扩展NativeWrapper - Library：'dart：ui'类：路径）

Answer 1

Hii 您的代码中有一个错误。据我从官方文档了解到 Isolate 的回调方法应该是顶级函数或static方法。 所以这个问题有两种解决方案。

解决方案 1. 将回调函数声明为顶级函数。

class MyHomePage extends StatelessWidget {
  final String title;

  const MyHomePage({Key? key, required this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(child: TextButton(
        child: const Text("Run Isolate"),
        onPressed: _onPressed,
      ));
    );
  }

  // Callback function for Text Button Event this should be a class member
  void _onPressed() async {
    var receivePort = ReceivePort();
    // Here runMyIsolate methos should be a top level function
    await Isolate.spawn(runMyIsolate, [receivePort.sendPort, "My Custom Message"]);
    print(await receivePort.first);
  }
}


// We declare a top level function here for an isolated callback function
void runMyIsolate(List<dynamic> args) {
  var sendPort = args[0] as SendPort;
  print("In runMyIsolate ");
  Isolate.exit(sendPort, args);
}

解决方案 2. 相反，我们可以将此函数声明为static同一类的函数，请考虑下面的示例。

    class MyHomePage extends StatelessWidget {
  final String title;

  const MyHomePage({Key? key, required this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(child: TextButton(
        child: const Text("Run Isolate"),
        onPressed: _onPressed,
      ));
    );
  }

  // Callback function for Text Button Event this should be a class member
  void _onPressed() async {
    var receivePort = ReceivePort();
    // Here runMyIsolate methos should be a top level function
    await Isolate.spawn(runMyIsolate, [receivePort.sendPort, "My Custom Message"]);
    print(await receivePort.first);
  }
  
  // We declare a static function here for an isolated callback function
  static void runMyIsolate(List<dynamic> args) {
    var sendPort = args[0] as SendPort;
    print("In runMyIsolate ");
    Isolate.exit(sendPort, args);
  }
}