尝试为垂直和水平方向添加gestureRecognizers。以下是修改后的代码：

import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';
import '../../widgets/headers/custom_app_bar.dart';

class InfoScreen extends StatefulWidget {
  final String url;
  final String title;

  InfoScreen({Key key, @required this.title, @required this.url})
      : super(key: key);

  @override
  State<StatefulWidget> createState() => _InfoScreenState();
}

class _InfoScreenState extends State<InfoScreen> {
  bool isLoading = true;
  final _key = UniqueKey();

  @override
  Widget build(BuildContext context) {
    WebViewController controller;
    return Scaffold(
      appBar: CustomAppBar(title: widget.title),
      body: Stack(
        children: <Widget>[
          WebView(
            key: _key,
            initialUrl: widget.url,
            javascriptMode: JavascriptMode.unrestricted,
            onWebViewCreated: (WebViewController webViewController) {
              controller = webViewController;
            },
            onPageFinished: (finish) {
              setState(() {
                isLoading = false;
              });
            },
            gestureRecognizers: Set()
              ..add(
                Factory<VerticalDragGestureRecognizer>(
                  () => VerticalDragGestureRecognizer(),
                ),
              )
              ..add(
                Factory<HorizontalDragGestureRecognizer>(
                  () => HorizontalDragGestureRecognizer(),
                ),
              )
              ..add(
                Factory<ScaleGestureRecognizer>(
                  () => ScaleGestureRecognizer(),
                ),
              ),
          ),
          isLoading
              ? Center(
                  child: CircularProgressIndicator(),
                )
              : Stack(),
        ],
      ),
    );
  }
}