xamarin android webview文件上传下载不起作用。请，我和c#在一起很舒服

WebView webView = new WebView(this);
webView.Settings.JavaScriptEnabled = true; // 启用JavaScript
webView.Settings.AllowFileAccess = true; // 允许文件访问
webView.Settings.AllowFileAccessFromFileURLs = true; // 允许通过文件URL访问
webView.Settings.AllowUniversalAccessFromFileURLs = true; // 允许通过文件URL进行跨域访问

public class MyWebChromeClient : WebChromeClient
{
    public override bool OnShowFileChooser(WebView webView, IValueCallback filePathCallback, FileChooserParams fileChooserParams)
    {
        // 处理文件选择逻辑
        return true;
    }
}

// 设置WebView的WebChromeClient
webView.SetWebChromeClient(new MyWebChromeClient());

public class MyWebViewClient : WebViewClient
{
    public override bool ShouldOverrideUrlLoading(WebView view, string url)
    {
        // 处理URL加载逻辑
        return false;
    }

    public override void OnDownloadStart(string url, string userAgent, string contentDisposition, string mimeType, long contentLength)
    {
        // 处理文件下载逻辑
    }
}

// 设置WebView的WebViewClient
webView.SetWebViewClient(new MyWebViewClient());