如何使设备后退按钮在flutter webview中转到上一页

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

WebviewScaffold(
  url: 'https://example.com', // 要加载的网页URL
  appBar: AppBar(
    title: Text('Webview'), // Webview的标题
  ),
  withJavascript: true, // 启用JavaScript
  withLocalStorage: true, // 启用本地存储
);

MethodChannel _channel = MethodChannel('webview/back');

@override
Widget build(BuildContext context) {
  return WillPopScope(
    onWillPop: () async {
      _channel.invokeMethod('goBack'); // 调用原生平台的方法来执行后退操作
      return false; // 返回false以阻止默认的后退行为
    },
    child: WebviewScaffold(
      // ...
    ),
  );
}

MethodChannel channel = new MethodChannel(getFlutterView(), "webview/back");
channel.setMethodCallHandler(new MethodChannel.MethodCallHandler() {
  @Override
  public void onMethodCall(MethodCall methodCall, MethodChannel.Result result) {
    if (methodCall.method.equals("goBack")) {
      if (webView.canGoBack()) {
        webView.goBack(); // 执行WebView的后退操作
      }
    }
  }
});