Flutter：如何使用path_provider将文件写入本地目录？

Question

我正在开发一个Flutter应用程序，需要将文件写入本地系统（iOS、Android和Web）。我在逻辑上遵循了读写文件的留档，并使用path_provider制作了一个小例子来测试功能：

import 'package:path_provider/path_provider.dart';

...

  void _testPathProvider() async {
      // Directory appDocDir = await getTemporaryDirectory(); // Using a different dir. not working either
      // String appDocPath = appDocDir.path;

      Directory appDocDir = await getApplicationDocumentsDirectory();
      String appDocPath = appDocDir.path;
      debugPrint('$appDocPath/my_file.txt');

      // Save in local file system
      var file = await File('$appDocPath/my_file.txt').writeAsString('hello!');
  }

这个测试函数只是通过一个按钮来调用，没有什么疯狂之处。但当我在浏览器中运行时

Error: MissingPluginException(No implementation found for method getApplicationDocumentsDirectory on channel plugins.flutter.io/path_provider)
    at Object.throw_ [as throw] (http://localhost:42561/dart_sdk.js:5067:11)
at MethodChannel._invokeMethod (http://localhost:42561/packages/flutter/src/services/restoration.dart.lib.js:1560:21)
    at _invokeMethod.next (<anonymous>)
    at http://localhost:42561/dart_sdk.js:40571:33
    at _RootZone.runUnary (http://localhost:42561/dart_sdk.js:40441:59)
    at _FutureListener.thenAwait.handleValue (http://localhost:42561/dart_sdk.js:35363:29)
    at handleValueCallback (http://localhost:42561/dart_sdk.js:35931:49)
    at Function._propagateToListeners (http://localhost:42561/dart_sdk.js:35969:17)
    at _Future.new.[_completeWithValue] (http://localhost:42561/dart_sdk.js:35817:23)
    at async._AsyncCallbackEntry.new.callback (http://localhost:42561/dart_sdk.js:35838:35)
    at Object._microtaskLoop (http://localhost:42561/dart_sdk.js:40708:13)
    at _startMicrotaskLoop (http://localhost:42561/dart_sdk.js:40714:13)
    at http://localhost:42561/dart_sdk.js:36191:9

似乎这个问题是众所周知的，已经遵循了这里和这里的建议，包括：

• 运行flatter clean并重新获取包裹
• 完全关闭应用程序并重新运行
• 将颤振升级至最新稳定状态
• 重新将path_provider添加到我的pubspec中。亚马尔

我正在使用最新版本的依赖项（path\u提供程序：^2.0.9）。

非常感谢您的帮助。

Answer 1

以下是评论中提到的data uri方法的示例：

import 'dart:html' as html;

  final bytes = utf8.encode('hello!');
  final dataUri = 'data:text/plain;base64,${base64.encode(bytes)}';
  html.document.createElement('a') as html.AnchorElement
    ..href = dataUri
    ..download = 'my_file.txt'
    ..dispatchEvent(html.Event.eventType('MouseEvent', 'click'));

确保该文件位于dart文件中，该文件仅在html可用时导入，或者最好使用package:universal_html。