CefSharp自定义SchemeHandler

Question

我使用CefSharp的SchemeHandler来从我的C#项目中获取资源.css,.js或者.png使用自定义URL的文件,例如custom://cefsharp/assets/css/style.css

我有2个自定义类来存档.

第一类,MyCustomSchemeHandlerFactory将是处理自定义Scheme的那个,它看起来像这样,其中"custom"将是自定义方案:

internal class MyCustomSchemeHandlerFactory : ISchemeHandlerFactory
{
    public const string SchemeName = "custom";

    public IResourceHandler Create(IBrowser browser, IFrame frame, string schemeName, IRequest request)
    {
        return new MyCustomSchemeHandler();
    }
}

我实现的下一个类是MyCustomSchemeHandler接收调用并输出响应,它看起来像这样:

internal class MyCustomSchemeHandler : IResourceHandler
{

    private static readonly IDictionary<string, string> ResourceDictionary;

    private string mimeType;
    private MemoryStream stream;

    static MyCustomSchemeHandler()
    {
        ResourceDictionary = new Dictionary<string, string>
        {
            { "/home.html", Properties.Resources.index},
            { "/assets/css/style.css", Properties.Resources.style}
        };
    }

    public Stream Stream { get; set; }
    public int StatusCode { get; set; }
    public string StatusText { get; set; }
    public string MimeType { get; set; }
    public NameValueCollection Headers { get; private set; }

    public Stream GetResponse(IResponse response, out long responseLength, out string redirectUrl)
    {
        redirectUrl = null;
        responseLength = -1;

        response.MimeType = MimeType;
        response.StatusCode = StatusCode;
        response.StatusText = StatusText;
        response.ResponseHeaders = Headers;

        var memoryStream = Stream as MemoryStream;
        if (memoryStream != null)
        {
            responseLength = memoryStream.Length;
        }

        return Stream;
    }

    public bool ProcessRequestAsync(IRequest request, ICallback callback)
    {
        // The 'host' portion is entirely ignored by this scheme handler.
        var uri = new Uri(request.Url);
        var fileName = uri.AbsolutePath;
        string resource;

        if (ResourceDictionary.TryGetValue(fileName, out resource) && !string.IsNullOrEmpty(resource))
        {
            var resourceHandler = ResourceHandler.FromString(resource);
            stream = (MemoryStream)resourceHandler.Stream;

            var fileExtension = Path.GetExtension(fileName);
            mimeType = ResourceHandler.GetMimeType(fileExtension);

            callback.Continue();
            return true;
        }
        else
        {
            callback.Dispose();
        }

        return false;
    }

    void GetResponseHeaders(IResponse response, out long responseLength, out string redirectUrl)
    {
        responseLength = stream == null ? 0 : stream.Length;
        redirectUrl = null;

        response.StatusCode = (int)HttpStatusCode.OK;
        response.StatusText = "OK";
        response.MimeType = mimeType;
    }

    bool ReadResponse(Stream dataOut, out int bytesRead, ICallback callback)
    {
        //Dispose the callback as it's an unmanaged resource, we don't need it in this case
        callback.Dispose();

        if (stream == null)
        {
            bytesRead = 0;
            return false;
        }

        //Data out represents an underlying buffer (typically 32kb in size).
        var buffer = new byte[dataOut.Length];
        bytesRead = stream.Read(buffer, 0, buffer.Length);

        dataOut.Write(buffer, 0, buffer.Length);

        return bytesRead > 0;
    }

    bool CanGetCookie(Cookie cookie)
    {
        return true;
    }

    bool CanSetCookie(Cookie cookie)
    {
        return true;
    }

    void Cancel()
    {

    }

}

在这个类里面,我已经定义了一个自定义资源字典,它将决定资源中的哪个文件将被使用,正如我在第一个例子中所述,custom://cefsharp/assets/css/style.css应该加载资源Properties.Resources.style,问题是一旦我输入特定的内容就没有任何东西被加载url,我试图输出mimeType并且它工作但不知何故文件本身将无法正确输出.我的实施有问题吗？

另外我试图以下列形式输出原始文件:

if (ResourceDictionary.TryGetValue(fileName, out resource) && !string.IsNullOrEmpty(resource))
{
    MessageBox.Show(resource);
}

它输出正确的文件没有任何问题.

要加载自定义Scheme,我在初始化CefSharp之前使用以下代码:

var settings = new CefSettings();
settings.RegisterScheme(new CefCustomScheme
{
    SchemeName = MyCustomSchemeHandlerFactory.SchemeName,
    SchemeHandlerFactory = new MyCustomSchemeHandlerFactory()
});

上面的类基于以下链接:MyCustomSchemeHandlerFactory:FlashResourceHandlerFactory.cs MyCustomSchemeHandler:CefSharpSchemeHandler.cs和ResourceHandler.cs

Answer 1

由于 Cefsharp 在过去几个月中发生了一些变化，因此这里提供了一种更新且更简单的处理“文件”协议的方法。我写了关于这个问题的博客文章。

您要添加的是您的方案处理程序及其工厂：

using System;
using System.IO;
using CefSharp;

namespace MyProject.CustomProtocol
{
    public class CustomProtocolSchemeHandler : ResourceHandler
    {
        // Specifies where you bundled app resides.
        // Basically path to your index.html
        private string frontendFolderPath;

        public CustomProtocolSchemeHandler()
        {
            frontendFolderPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "./bundle/");
        }

        // Process request and craft response.
        public override bool ProcessRequestAsync(IRequest request, ICallback callback)
        {
            var uri = new Uri(request.Url);
            var fileName = uri.AbsolutePath;

            var requestedFilePath = frontendFolderPath + fileName;

            if (File.Exists(requestedFilePath))
            {
                byte[] bytes = File.ReadAllBytes(requestedFilePath);
                Stream = new MemoryStream(bytes);

                var fileExtension = Path.GetExtension(fileName);
                MimeType = GetMimeType(fileExtension);

                callback.Continue();
                return true;
            }

            callback.Dispose();
            return false;
        }
    }

    public class CustomProtocolSchemeHandlerFactory : ISchemeHandlerFactory
    {
        public const string SchemeName = "customFileProtocol";

        public IResourceHandler Create(IBrowser browser, IFrame frame, string schemeName, IRequest request)
        {
            return new CustomProtocolSchemeHandler();
        }
    }
}

然后在调用Cef.Initialize之前注册它：

var settings = new CefSettings
{
  BrowserSubprocessPath = GetCefExecutablePath()
};

settings.RegisterScheme(new CefCustomScheme
{
  SchemeName = CustomProtocolSchemeHandlerFactory.SchemeName,
  SchemeHandlerFactory = new CustomProtocolSchemeHandlerFactory()
});

Answer 2

如果您只需要返回一个字符串，那么您可以使用ResourceHandler.FromString(html, mimeType). 为此，您只需实施ISchemeHandlerFactory.

https://github.com/cefsharp/CefSharp/blob/cefsharp/47/CefSharp/ResourceHandler.cs#L98

从文件读取的示例https://github.com/cefsharp/CefSharp/blob/cefsharp/47/CefSharp.Example/CefSharpSchemeHandlerFactory.cs#L17可以非常简单地转换为从字符串读取。