How can I solve this problem? Can someone please help me?

[AriBermeki]

Error @ use_custom_protocol (handler)

mismatched types
expected struct `Box<(dyn std::ops::Fn(wry::http::Request<Vec<u8>>, RequestAsyncResponder) + 'static)>`
   found struct `Box<(dyn std::ops::Fn(wry::http::Request<Vec<u8>>, RequestAsyncResponder) -> Response<Vec<u8>> + 'static)>

fn get_nexium_response_protocol(
    request: Request<Vec<u8>>,
    index_page:Option<String>, 
    root_path: &PathBuf
) -> Result<Response<Vec<u8>>, Box<dyn std::error::Error>> {
    let path = request.uri().path();
    // Read the file content from file path

    let path = if path == "/" {
        index_page.unwrap_or_else(|| "index.html".into())
    } else {
        // Removing leading slash and converting to String
        path[1..].to_string()
    };
    let full_path = std::fs::canonicalize(root_path.join(path))?;
    let content = std::fs::read(&full_path)?;
    #[cfg(target_os = "windows")]
    let headers = "https://wry.localhost".to_string();
    #[cfg(not(target_os = "windows"))]
    let headers = "wry://localhost".to_string();
    // Determine MIME type using `mime_guess`
    let mime_type = from_path(&full_path).first_or_octet_stream();

    Response::builder()
        .header(CONTENT_TYPE, mime_type.as_ref())
        .header("Access-Control-Allow-Origin", headers)
        .header("Cache-Control", "no-cache, no-store, must-revalidate")
        .header("Pragma", "no-cache")
        .header("Expires", "0")
        .header("Accept-Encoding", "gzip, compress, br, deflate")
        .body(content)
        .map_err(Into::into)
}
    pub fn use_custom_protocol(
        &mut self,
        index_page: &str,
        protocol_name: Option<String>,
        url: Option<String>, // Ändern des Typs auf Option<String>
        path: &str,
    ) {
        let protocol_name = protocol_name.unwrap_or_else(|| "wry".into());
    
        let handler: Box<dyn Fn(Request<Vec<u8>>, RequestAsyncResponder) -> Response<Vec<u8>> + 'static> = 
            Box::new(move |request, responder| {
                let path = PathBuf::new().join(path);
                match get_nexium_response_protocol(request, Some(index_page.to_string()), &path) {
                    Ok(r) => r.map(Into::into),
                    Err(e) => Response::builder()
                        .header(CONTENT_TYPE, "text/plain")
                        .status(500)
                        .body(e.to_string().as_bytes().to_vec())
                        .unwrap()
                        .map(Into::into),
                }
            });
    
        self.webview_core.custom_protocols.push((
            protocol_name,
            handler,
        ));
        let host_url = url.unwrap_or_else(|| "wry://localhost".into());
        self.webview_core.url = Some(host_url);
        self.webview_core.headers = None;
    }

[FabianLars]

Your syntax seems to be for sync custom protocols while you're trying to register an async protocol.

The async protocol handler can't return values. Instead you'll have to use the responder to "respond" (return values).

Apart from the small doc example, we also have a full example here: https://github.com/tauri-apps/wry/blob/dev/examples/async_custom_protocol.rs#L44-L45