Flutter：如何使用 path_provider 将文件写入本地目录？

Question

我正在开发 Flutter 应用程序，需要将文件写入本地系统（iOS、Android 以及 Web）。我在逻辑上遵循了 Read and Write Files, and used path_provider 上的文档来制作一个小示例来测试功能：

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调用，没有什么疯狂的。但是当我运行在浏览器中跳动并按下按钮时，我收到以下错误：

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，已遵循 and here 的建议，包括：

运行ning flutter clean 并重新获取包
完全关闭应用程序并重新运行宁
正在将 Flutter 升级到最新的稳定版
重新添加 path_provider 到我的 pubspec.yaml

我正在使用最新版本的依赖项 (path_provider: ^2.0.9)。

非常感谢任何帮助。

Answer 1

下面是评论中提到的data uri方法的例子：

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'));

确保它位于仅在 html 可用时导入的 dart 文件中，或者最好使用 package:universal_html.

Flutter：如何使用 path_provider 将文件写入本地目录？

Flutter: how do I write a file to local directory with path_provider?

flutter

flutter-dependencies

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