在任何文件 load/processing 之前注入 CefSharp Javascript

Question

对于我正在进行的项目，我需要在任何网页文档处理开始之前注入 javascript。这可以通过 WebBrowser 组件轻松实现，但我在使用 CefSharp 时遇到困难。

这里是问题的简化，网页需要 "InjectedObject" 才能正常运行。在文档的最顶部调用没有注入的网页，或者在处理文档之前 evaluated/executed 将导致：

=====html 失败时的示例输出=====

是否存在对象？

错误

=====

我需要显示网页的地方：

=====html 成功时的示例输出=====

是否存在对象？

正确

=====

<html>
  <head>
    <script>
      isObjectPresent = typeof InjectedObject == "object";
    </script>
  </head>
  <body>
    <p>isObjectPresent?</p>
    <div id="result"></div>
    <script>
      document.getElementById("result").innerHTML = isObjectPresent;
    </script>
  </body>
</html>

查看所有可用的建议表明我应该使用 LoadingStateChanged() 或 FrameLoadEnd() 来注入脚本，即：

public void OnFrameLoadEnd(object sender, FrameLoadEndEventArgs args) {
  if (args.Frame.IsMain) {
    args.Frame.ExecuteJavascriptAsync("window.InjectedObject = {};");
  }
}

然而，我尝试过的所有迭代，甚至使用 FrameLoadStart，都导致在文档开始处理后插入 javascript。是否有任何真正的 javascript 注入示例可确保它在文档处理开始之前发生。（确保避免比赛 condition/timing 问题）。

作为我想要模仿的 WebBrowser 组件行为的示例是：

private void uiWebBrowser_Navigated(object sender, System.Windows.Navigation.NavigationEventArgs e) 
{
  var browser = (WebBrowser)sender;
  var document = browser.Document as HTMLDocument;
  var head = document.getElementsByTagName("head").Cast<HTMLHeadElement>().First();
  if (head != null)
  {
    var script = document.createElement("script") as IHTMLScriptElement;
    script.text = "window.InjectedObject = {};"
    if (head.firstChild != null)
    {
      head.insertBefore((IHTMLDOMNode)script, head.firstChild);
    }
    else
    {
      head.appendChild((IHTMLDOMNode)script;
    }
  }
}

欢迎任何帮助或建议，理想情况下我想避免通过互联网请求解析和插入下载页面，然后使用加载html，因为我预计我可能不得不这样做对于影响主框架的所有导航操作，这听起来像是一项 hack 工作。

根据评论，建议 javascript V8 引擎上下文足以满足上述用例。尝试从 IRenderProcessMessageHandler 接口实现 OnContextCreated 方法具有相同的结果。

==MainWindow.xaml==

<Window x:Class="ExampleCefSharp001.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:cefSharp="clr-namespace:CefSharp.Wpf;assembly=CefSharp.Wpf"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:ExampleCefSharp001"
    mc:Ignorable="d"
    Title="MainWindow" Height="1000" Width="1100">
  <Grid>
    <cefSharp:ChromiumWebBrowser x:Name="uiWebView"></cefSharp:ChromiumWebBrowser>
  </Grid>
</Window>

==MainWindow.xaml.cs==

public partial class MainWindow : Window
{
  JavascriptManager jsmanager;

  public MainWindow()
  {
    InitializeComponent();

    jsmanager = new JavascriptManager(uiWebView);
  }
}

public class JavascriptManager : ILoadHandler, IRenderProcessMessageHandler
{
  string injection = "window.InjectedObject = {};";

  public JavascriptManager(ChromiumWebBrowser browser)
  {
    browser.LoadHandler = this;
    browser.RenderProcessMessageHandler = this;

    //  Lets just pretend this is a real url with the example html above.
    browser.Address = "https://www.example.com/timingtest.htm"
  }

  public void OnContextCreated(IWebBrowser browserControl, IBrowser browser, IFrame frame)
  {
    frame.ExecuteJavaScriptAsync(injection);
  }
}

非常感谢您提出的意见和建议。如果我遗漏了什么，请告诉我！

Answer 1

终于回到了这里。主要基于以下示例：CefSharp.Example/Filters/FindReplaceResponseFilter.cs

实现 IRequestHandler 和 IResponseFilter 接口：

==MainWindow.xaml==

<Window x:Class="ExampleCefSharp001.MainWindow"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:cefSharp="clr-namespace:CefSharp.Wpf;assembly=CefSharp.Wpf"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
  xmlns:local="clr-namespace:ExampleCefSharp001"
  mc:Ignorable="d"
  Title="MainWindow" Height="1000" Width="1100">
  <Grid>
    <cefSharp:ChromiumWebBrowser x:Name="uiWebView"></cefSharp:ChromiumWebBrowser>
  </Grid>
</Window>

==MainWindow.xaml.cs==

public partial class MainWindow : Window
{
  JavascriptManager jsmanager;

  public MainWindow()
  {
    InitializeComponent();

    jsmanager = new JavascriptManager(uiWebView);
  }
}

public class JavascriptManager : IRequestHandler
{
  string injection = "window.InjectedObject = {};";

  public JavascriptManager(ChromiumWebBrowser browser)
  {
    browser.RequestHandler = this;

    //  Lets just pretend this is a real url with the example html above.
    browser.Address = "https://www.example.com/timingtest.htm"
  }

  public IResponseFilter GetResourceResponseFilter(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response)
    {
        if (frame.IsMain && request.ResourceType == ResourceType.MainFrame) 
        {
            return new JavascriptInjectionFilter(injection);
        }
        return null;
    }
}

public class JavascriptInjectionFilter : IResponseFilter
{
    /// <summary>
    /// Location to insert the javascript
    /// </summary>
    public enum Locations
    {
        /// <summary>
        /// Insert Javascript at the top of the header element
        /// </summary>
        head,
        /// <summary>
        /// Insert Javascript at the top of the body element
        /// </summary>
        body
    }

    string injection;
    string location;
    int offset = 0;
    List<byte> overflow = new List<byte>();

    /// <summary>
    /// Constructor
    /// </summary>
    /// <param name="injection"></param>
    /// <param name="location"></param>
    public JavascriptInjectionFilter(string injection, Locations location = Locations.head)
    {
        this.injection = "<script>" + injection + "</script>";
        switch (location)
        {
            case Locations.head:
                this.location = "<head>";
                break;

            case Locations.body:
                this.location = "<body>";
                break;

            default:
                this.location = "<head>";
                break;
        }
    }

    /// <summary>
    /// Disposal
    /// </summary>
    public void Dispose()
    {
        //
    }

    /// <summary>
    /// Filter Processing...  handles the injection
    /// </summary>
    /// <param name="dataIn"></param>
    /// <param name="dataInRead"></param>
    /// <param name="dataOut"></param>
    /// <param name="dataOutWritten"></param>
    /// <returns></returns>
    public FilterStatus Filter(Stream dataIn, out long dataInRead, Stream dataOut, out long dataOutWritten)
    {
        dataInRead = dataIn == null ? 0 : dataIn.Length;
        dataOutWritten = 0;

        if (overflow.Count > 0)
        {
            var buffersize = Math.Min(overflow.Count, (int)dataOut.Length);
            dataOut.Write(overflow.ToArray(), 0, buffersize);
            dataOutWritten += buffersize;

            if (buffersize < overflow.Count)
            {
                overflow.RemoveRange(0, buffersize - 1);
            }
            else
            {
                overflow.Clear();
            }
        }


        for (var i = 0; i < dataInRead; ++i)
        {
            var readbyte = (byte)dataIn.ReadByte();
            var readchar = Convert.ToChar(readbyte);
            var buffersize = dataOut.Length - dataOutWritten;

            if (buffersize > 0)
            {
                dataOut.WriteByte(readbyte);
                dataOutWritten++;
            }
            else
            {
                overflow.Add(readbyte);
            }

            if (char.ToLower(readchar) == location[offset])
            {
                offset++;
                if (offset >= location.Length)
                {
                    offset = 0;
                    buffersize = Math.Min(injection.Length, dataOut.Length - dataOutWritten);

                    if (buffersize > 0)
                    {
                        var data = Encoding.UTF8.GetBytes(injection);
                        dataOut.Write(data, 0, (int)buffersize);
                        dataOutWritten += buffersize;
                    }

                    if (buffersize < injection.Length)
                    {
                        var remaining = injection.Substring((int)buffersize, (int)(injection.Length - buffersize));
                        overflow.AddRange(Encoding.UTF8.GetBytes(remaining));
                    }

                }
            }
            else
            {
                offset = 0;
            }

        }

        if (overflow.Count > 0 || offset > 0)
        {
            return FilterStatus.NeedMoreData;
        }

        return FilterStatus.Done;
    }

    /// <summary>
    /// Initialization
    /// </summary>
    /// <returns></returns>
    public bool InitFilter()
    {
        return true;
    }

}

感谢 amaitland 为我指明了正确的方向，并感谢上面大部分代码所基于的示例程序。最终结果：

<html><head></head><body><script>window.InjectedObject = {}</script>
  <script>
    isObjectPresent = typeof InjectedObject == "object";
  </script>
  <p>isObjectPresent?</p>
  <div id="result"></div>
  <script>
    document.getElementById("result").innerHTML = isObjectPresent;
  </script>
</body></html>

这满足了我对 pre-processing 文档的需求，在 header 的顶部有一些文本确保现有代码可能运行在注入代码之前没有时间问题。

编辑几个小修复。添加控制逻辑以仅在加载大型机时插入。

Answer 2

你的答案是正确的，你应该重写 GetResourceResponseFilter 的实现，但如果你没有以正确的方式实现接口，你最终会导致浏览器不呈现内容，你可以改为继承DefaultRequestHandler 并覆盖 GetResourceResponseFilter() 并提供已接受答案中提到的自定义过滤器，如果您只需要验证此特定功能，这将更容易：

public class CustomRequestHandler : DefaultRequestHandler
{
    string script = "alert('hello');";

    public override IResponseFilter GetResourceResponseFilter(CefSharp.IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response)
    {
        if (frame.IsMain && request.ResourceType == ResourceType.MainFrame)
        {
            return new JavascriptInjectionFilter(script);
        }
        return null;
    }
}

然后赋给chromium浏览器：

CustomRequestHandler customRequestHandler = new CustomRequestHandler();
chromeBrowser.RequestHandler = customRequestHandler ;

在任何文件 load/processing 之前注入 CefSharp Javascript

CefSharp Inject Javascript prior to any document load/processing

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