我无法通过本地html文件在flutter webview中加载传单地图

flutter:
  assets:
    - assets/my_html_file.html

dependencies:
  flutter:
    sdk: flutter
  webview_flutter: ^2.0.0

import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';

class MyWebView extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('WebView'),
      ),
      body: WebView(
        initialUrl: 'file:///android_asset/flutter_assets/assets/my_html_file.html',
        javascriptMode: JavascriptMode.unrestricted,
      ),
    );
  }
}