CefSharp在任何文档加载/处理之前注入Javascript

问题描述 投票：6回答：2

对于我正在处理的项目，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时遇到了困难。

这是问题的简化，网页需要“InjectedObject”才能运行。在文档的最顶部调用未注入的网页，或者在处理文档之前进行评估/执行将导致：

===== html示例输出失败=====

isObjectPresent？

假

=====

我需要在哪里显示网页：

===== html示例输出成功=====

isObjectPresent？

真正

=====

<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将表明我应该使用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出现插入的javascript。是否有任何真正的javascript注入示例确保它在文档处理开始之前发生。 （确保避免竞争条件/时间问题）。

作为我想模仿的WebBrowser组件行为的一个例子是：

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;
    }
  }
}

任何帮助或建议都是受欢迎的，理想情况下我希望避免通过互联网请求解析和插入，然后使用loadhtml下载页面，因为我希望我可能必须为影响主框架的所有导航操作做到这一点，这听起来像一个黑客工作。

从评论中得出结论，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);
  }
}

我非常感谢您的意见和建议。如果有什么我遗失的请告诉我！

javascript c# cefsharp javascript-injection
2个回答
5
投票

终于回到了这个。严重基于以下示例：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指出我正确的方向，以及上面代码绝大部分基于的示例程序。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>

这满足了我对文档进行预处理的需要，并在标题的顶部添加了一些文本，确保在注入的代码之前可以运行现有代码的时间问题。

编辑几个小修复。添加了控制逻辑，仅在加载主机时插入。

1
投票

那你的答案是正确的，你应该覆盖GetResourceResponseFilter的实现，但如果你没有以正确的方式实现接口，你最终将浏览器不渲染内容，你可以改为继承DefaultRequestHandler并覆盖GetResourceResponseFilter()并提供在接受的答案中提到的自定义过滤器，如果您只需要完成此特定功能，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;
    }
}

然后将其分配给chrome浏览器：

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