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javascript - CefSharp 在任何文档加载/处理之前注入(inject) Javascript

转载 作者：数据小太阳 更新时间：2023-10-29 04:14:29 27 4
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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(inject) javascript。这可以通过 WebBrowser 组件轻松实现，但我在使用 CefSharp 时遇到困难。

这里是问题的一个简化，网页需要一个“InjectedObject”才能发挥作用。调用网页而不注入(inject)发生在文档的最顶部，或者在处理文档之前被评估/执行将导致:

=====失败时的 html 示例输出=====

存在对象吗？

错误

=====

我需要显示网页的地方:

=====成功时的 html 示例输出=====

存在对象吗？

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(inject)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，都导致插入的 javascript 在文档开始处理后发生。是否有任何真正的 javascript 注入(inject)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 loadhtml，因为我希望我可能必须为影响的所有导航操作执行此操作主框架，这听起来像是一项黑客工作。

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(interface)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);
  }
}

非常感谢您的意见和建议。如果我遗漏了什么，请告诉我!

最佳答案

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(interface):

==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，并为上面绝大多数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>

这满足了我在标题顶部使用一些文本预处理文档的需求，确保在注入(inject)代码之前运行现有代码时不会出现计时问题。

编辑几个小修复。添加控制逻辑以仅在加载大型机时插入。

关于javascript - CefSharp 在任何文档加载/处理之前注入(inject) Javascript，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/41745827/

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