CefSharp过滤图片RequestHandler问题

C# CefSharp 过滤 RequestHandler 图片

1、方式一

ChromiumWebBrowser 实现 IRequestHandler

具体内同参照 附录；将 OnBeforeResourceLoad方法替换成2中的内容，很简单；

2、方式二

继承集成默认的抽象类 DefaultRequestHandler

 internal class RequestHandler : DefaultRequestHandler 
    {

        public  override CefReturnValue  OnBeforeResourceLoad(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IRequestCallback callback)
        {

            if (request.ResourceType == ResourceType.Image)
                return CefReturnValue.Cancel;

            return CefReturnValue.Continue;
        }
}

对比实现接口方式和继承集成默认的抽象类，发现抽象类可以只实现相关的处理方法更加灵活。而若采用IRequestHandler需要实现RequestHandler接口中的所有方法，否则抛出未实现异常；

和其他网上从Response环节过滤资源图片的方法不同，这里谈到的方法在请求图片资源之前，可以节省流量，加快页面访问速度等。

附录：

using System;
using CefSharp.Example.Filters;
using System.Security.Cryptography.X509Certificates;
using System.Collections.Generic;
using System.Text;
using CefSharp.Handler;

namespace CefSharp.Example.Handlers
{
   /// <summary>
   /// DefaultRequestHandler provides a base class for you to inherit from
   /// you only need to implement the methods that are relevant to you.
   /// If you implement the IRequestHandler interface you will need to
   /// implement every method
   /// </summary>
   public class RequestHandler : IRequsetHandler
   {
       public static readonly string VersionNumberString = String.Format("Chromium: {0}, CEF: {1}, CefSharp: {2}",
           Cef.ChromiumVersion, Cef.CefVersion, Cef.CefSharpVersion);

private Dictionary<UInt64, MemoryStreamResponseFilter> responseDictionary = new Dictionary<UInt64, MemoryStreamResponseFilter>();

public override bool OnBeforeBrowse(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, bool userGesture, bool isRedirect)
       {
           return false;
       }

public override bool OnOpenUrlFromTab(IWebBrowser browserControl, IBrowser browser, IFrame frame, string targetUrl, WindowOpenDisposition targetDisposition, bool userGesture)
       {
           return false;
       }

public override bool OnCertificateError(IWebBrowser browserControl, IBrowser browser, CefErrorCode errorCode, string requestUrl, ISslInfo sslInfo, IRequestCallback callback)
       {
           //NOTE: If you do not wish to implement this method returning false is the default behaviour
           // We also suggest you explicitly Dispose of the callback as it wraps an unmanaged resource.
           //callback.Dispose();
           //return false;

//NOTE: When executing the callback in an async fashion need to check to see if it's disposed
           if (!callback.IsDisposed)
           {
               using (callback)
               {
                   //To allow certificate
                   //callback.Continue(true);
                   //return true;
               }
           }

return false;
       }

public override void OnPluginCrashed(IWebBrowser browserControl, IBrowser browser, string pluginPath)
       {
           // TODO: Add your own code here for handling scenarios where a plugin crashed, for one reason or another.
       }

public override CefReturnValue OnBeforeResourceLoad(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IRequestCallback callback)
       {
           Uri url;
           if (Uri.TryCreate(request.Url, UriKind.Absolute, out url) == false)
           {
               //If we're unable to parse the Uri then cancel the request
               // avoid throwing any exceptions here as we're being called by unmanaged code
               return CefReturnValue.Cancel;
           }

//Example of how to set Referer
           // Same should work when setting any header

// For this example only set Referer when using our custom scheme
           if (url.Scheme == CefSharpSchemeHandlerFactory.SchemeName)
           {
               //Referrer is now set using it's own method (was previously set in headers before)
               request.SetReferrer("http://google.com", ReferrerPolicy.Default);
           }

//Example of setting User-Agent in every request.
           //var headers = request.Headers;

//var userAgent = headers["User-Agent"];
           //headers["User-Agent"] = userAgent + " CefSharp";

//request.Headers = headers;

//NOTE: If you do not wish to implement this method returning false is the default behaviour
           // We also suggest you explicitly Dispose of the callback as it wraps an unmanaged resource.
           //callback.Dispose();
           //return false;

//NOTE: When executing the callback in an async fashion need to check to see if it's disposed
           if (!callback.IsDisposed)
           {
               using (callback)
               {
                   if (request.Method == "POST")
                   {
                       using (var postData = request.PostData)
                       {
                           if(postData != null)
                           {
                               var elements = postData.Elements;

var charSet = request.GetCharSet();

foreach (var element in elements)
                               {
                                   if (element.Type == PostDataElementType.Bytes)
                                   {
                                       var body = element.GetBody(charSet);
                                   }
                               }
                           }
                       }
                   }

//Note to Redirect simply set the request Url
                   //if (request.Url.StartsWith("https://www.google.com", StringComparison.OrdinalIgnoreCase))
                   //{
                   //    request.Url = "https://github.com/";
                   //}

//Callback in async fashion
                   //callback.Continue(true);
                   //return CefReturnValue.ContinueAsync;
               }
           }

return CefReturnValue.Continue;
       }

public override bool GetAuthCredentials(IWebBrowser browserControl, IBrowser browser, IFrame frame, bool isProxy, string host, int port, string realm, string scheme, IAuthCallback callback)
       {
           //NOTE: If you do not wish to implement this method returning false is the default behaviour
           // We also suggest you explicitly Dispose of the callback as it wraps an unmanaged resource.

callback.Dispose();
           return false;
       }

public override bool OnSelectClientCertificate(IWebBrowser browserControl, IBrowser browser, bool isProxy, string host, int port, X509Certificate2Collection certificates, ISelectClientCertificateCallback callback)
       {
           //NOTE: If you do not wish to implement this method returning false is the default behaviour
           // We also suggest you explicitly Dispose of the callback as it wraps an unmanaged resource.
           callback.Dispose();
           return false;
       }

public override void OnRenderProcessTerminated(IWebBrowser browserControl, IBrowser browser, CefTerminationStatus status)
       {
           // TODO: Add your own code here for handling scenarios where the Render Process terminated for one reason or another.
           browserControl.Load(CefExample.RenderProcessCrashedUrl);
       }

public override bool OnQuotaRequest(IWebBrowser browserControl, IBrowser browser, string originUrl, long newSize, IRequestCallback callback)
       {
           //NOTE: If you do not wish to implement this method returning false is the default behaviour
           // We also suggest you explicitly Dispose of the callback as it wraps an unmanaged resource.
           //callback.Dispose();
           //return false;

//NOTE: When executing the callback in an async fashion need to check to see if it's disposed
           if (!callback.IsDisposed)
           {
               using (callback)
               {
                   //Accept Request to raise Quota
                   //callback.Continue(true);
                   //return true;
               }
           }

return false;
       }

public override void OnResourceRedirect(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response, ref string newUrl)
       {
           //Example of how to redirect - need to check `newUrl` in the second pass
           //if (request.Url.StartsWith("https://www.google.com", StringComparison.OrdinalIgnoreCase) && !newUrl.Contains("github"))
           //{
           //    newUrl = "https://github.com";
           //}
       }

public override bool OnProtocolExecution(IWebBrowser browserControl, IBrowser browser, string url)
       {
           return url.StartsWith("mailto");
       }

public override void OnRenderViewReady(IWebBrowser browserControl, IBrowser browser)
       {

}

public override bool OnResourceResponse(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response)
       {
           //NOTE: You cannot modify the response, only the request
           // You can now access the headers
           //var headers = response.Headers;

return false;
       }

public override IResponseFilter GetResourceResponseFilter(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response)
       {
           var url = new Uri(request.Url);
           if (url.Scheme == CefSharpSchemeHandlerFactory.SchemeName)
           {
               if(request.Url.Equals(CefExample.ResponseFilterTestUrl, StringComparison.OrdinalIgnoreCase))
               {
                   return new FindReplaceResponseFilter("REPLACE_THIS_STRING", "This is the replaced string!");
               }

if (request.Url.Equals("custom://cefsharp/assets/js/jquery.js", StringComparison.OrdinalIgnoreCase))
               {
                   return new AppendResponseFilter(System.Environment.NewLine + "//CefSharp Appended this comment.");
               }

//Only called for our customScheme
               var dataFilter = new MemoryStreamResponseFilter();
               responseDictionary.Add(request.Identifier, dataFilter);
               return dataFilter;
           }

//return new PassThruResponseFilter();
           return null;
       }

public override void OnResourceLoadComplete(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response, UrlRequestStatus status, long receivedContentLength)
       {
           var url = new Uri(request.Url);
           if (url.Scheme == CefSharpSchemeHandlerFactory.SchemeName)
           {
               MemoryStreamResponseFilter filter;
               if(responseDictionary.TryGetValue(request.Identifier, out filter))
               {
                   //TODO: Do something with the data here
                   var data = filter.Data;
                   var dataLength = filter.Data.Length;
                   //NOTE: You may need to use a different encoding depending on the request
                   var dataAsUtf8String = Encoding.UTF8.GetString(data);                
               }
           }
       }
   }
}

来源：https://blog.csdn.net/qq_34061547/article/details/82390279