不支持的操作:在web上使用dart io时出现_Namespace

Question

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)

代码我使用了最终输出= io.File('output.txt').openWrite()；output.write(output_data)；

Could you please help me in fixing it.
Or any other way to read and write files using dart in a web application.

Answer 1

不能在web项目中使用dart:io。dart:html有一些有限的文件应用编程接口(限于浏览器允许的范围)。浏览器中的Dart不能执行浏览器未提供的任何操作。

(不确定为什么Günter没有把这个作为答案...)

Answer 2

if (kIsWeb) {
  image = Image.network(pickedFile.path);
} else {
  image = Image.file(File(pickedFile.path));
}

答案在documentation https://pub.dev/packages/image_picker中

Answer 3

使用https://pub.dev/packages/image_picker库。

在dart文件中：

import 'dart:io';

对于选择图像，请使用以下代码：

_imgFromGallery() async {
   final temp = (await ImagePicker().
                 getImage(source:ImageSource.camera,imageQuality: 
                 80));
   imageForSendToAPI = await temp.readAsBytes();
   setState(() {});
  }

此方法将从桌面获取图像。

这里imageForSendToAPI会给你一个uint8list，你可以把它传给API。

用于显示所选文件的使用情况：

Image.memory(imageForSendToAPI)

对于发送到API，不要使用multipart，只需像下面这样传递：

data = {
"profile_image":imageForsendToAPI.toString();
}