相关疑难解决方法(0)

I am trying to use dart-io to read and write file. I am getting below exception.
Uncaught Error: Unsupported operation: _Namespace
    at Object.dart.throw (dart_sdk.js:4537)
    at Function.get _namespacePointer [as _namespacePointer] (dart_sdk.js:49364)
    at Function._namespacePointer (dart_sdk.js:47224)
    at Function._dispatchWithNamespace (dart_sdk.js:47227)
    at io._File.new.open (dart_sdk.js:47342)
    at new io._FileStreamConsumer.new (dart_sdk.js:47186)
    at io._File.new.openWrite (dart_sdk.js:47468)
    at refresh (main.dart:15)
    at refresh.next (<anonymous>)
    at runBody (dart_sdk.js:22264)
    at Object.async.async (dart_sdk.js:22292)
    at main.refresh (main.dart:13)
    at Object.dart._checkAndCall (dart_sdk.js:4731)
    at Object.dart.dcall (dart_sdk.js:4736)

我使用的代码最终输出 = io.File('output.txt').openWrite(); output.write(output_data);

Could you please help me in fixing it.
Or …

这个问题是上一个问题的延续。我编写了以下代码来确定是否File.openRead()创建了可以逐行流式传输的 Stream。事实证明答案是否定的。读取整个文件，然后传递到下一个转换。我的问题是：如何在 Dart 中逐行流式传输文件？

import 'dart:async';
import 'dart:convert';
import 'dart:io';


void main(List<String> arguments) {

  Stream<List<int>> stream = new File('Data.txt').openRead();

   stream
      .transform(const Utf8InterceptDecoder())
        .transform(const LineSplitterIntercept())
          .listen((line) {
//            stdout.writeln(line);
          }).asFuture().catchError((_) => print(_));
}

int lineSplitCount = 0;

class LineSplitterIntercept extends LineSplitter {

  const LineSplitterIntercept() : super();
  // Never gets called
  List<String> convert(String data) {
    stdout.writeln("LineSplitterIntercept.convert : Data:" + data);
    return super.convert(data);
  }

  StringConversionSink startChunkedConversion(ChunkedConversionSink<String> sink) {
    stdout.writeln("LineSplitterIntercept.startChunkedConversion Count:"+lineSplitCount.toString()+ " Sink: " + sink.toString());
    lineSplitCount++;
    return super.startChunkedConversion(sink);
  }
} …