如何向 dart js 门面添加扩展

Question

我正在尝试将 showOpenFilePicker 添加到 Window 对象。

  @JS()
library js_t;

import 'dart:html';

import 'package:js/js.dart'; 

@JS("window")
abstract class _Window2 {
  external dynamic showOpenFilePicker();
}
    
extension WindowExt on Window {
      Future<dynamic> showOpenFilePicker() {
        Object t = this;
        final _Window2 tt = t;
        return promiseToFuture(tt.showOpenFilePicker());
      }
 }
 final r = await window.showOpenFilePicker();

我收到以下错误

errors.dart:187 Uncaught Error: Expected a value of type 'JSObject<>', but got one of type 'Window' at Object.throw_ [as throw] (errors.dart:233) at Object.castError (errors.dart:84) at Object.cast [as as] (operations.dart:442) at dart.LegacyType.new.as (types.dart:445) at Object.WindowExt4showOpenFilePicker [as WindowExt|showOpenFilePicker] (js_t.dart:36) at main$ (main.dart:12)

Answer 1

这个对我有用

extension WindowExt on Window {
  @JS("window.showOpenFilePicker")
  external dynamic _showOpenFilePicker();

  Future<dynamic> showOpenFilePicker() {
    return promiseToFuture(_showOpenFilePicker());
  }
}

编辑：

但来自文档

/// An annotation that indicates a library, class, or member is implemented
/// directly in JavaScript.
///
/// All external members of a class or library with this annotation implicitly
/// have it as well.
///
/// Specifying [name] customizes the JavaScript name to use. By default the
/// dart name is used. It is not valid to specify a custom [name] for class
/// instance members.
class JS {
  final String? name;
  const JS([this.name]);
}

为 class 指定自定义 [name] 无效 /// 实例成员.

:s

编辑2：

js_utils 求救

extension WindowExt on Window {
 Future<dynamic> showOpenFilePicker() {
    final Object t = this;
    return promiseToFuture(callMethod(t, "showOpenFilePicker", []));
  }
}

如何向 dart js 门面添加扩展

how to add extensions to dart js facades

dart

dart-html