有没有办法在Flutter WebView中导入外部脚本

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

class MyWebView extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return WebviewScaffold(
      url: 'https://example.com',
      withJavascript: true,
      javascriptChannels: <JavascriptChannel>[
        _createJavascriptChannel(context),
      ].toSet(),
    );
  }

  JavascriptChannel _createJavascriptChannel(BuildContext context) {
    return JavascriptChannel(
      name: 'ExternalScriptChannel',
      onMessageReceived: (JavascriptMessage message) {
        // 处理来自WebView的消息
        String scriptResult = message.message;
        // 在这里可以对脚本执行结果进行处理
      },
    );
  }
}

WebviewScaffold(
  url: 'https://example.com',
  withJavascript: true,
  javascriptChannels: <JavascriptChannel>[
    _createJavascriptChannel(context),
  ].toSet(),
  onPageFinished: (String url) {
    // WebView加载完成后执行注入脚本的操作
    webViewPlugin.evalJavascript('''
      var script = document.createElement('script');
      script.src = 'https://example.com/external_script.js';
      document.head.appendChild(script);
    ''');
  },
);

window.ExternalScriptChannel.postMessage('Hello from external script!');