如何从 UIWEBVIEW 下载 xls 格式的文件？

问：

- (BOOL) webView:(UIWebView *) webView shouldStartLoadWithRequest:(NSURLRequest *) request navigationType:(UIWebViewNavigationType) navigationType
{
     
    NSString *mimeType = [request valueForHTTPHeaderField:@"Content-Type"];
    NSLog(@"Content-type: %@", mimeType);
    if(mimeType isEqualToString:@"application/vnd.ms-excel"] )
    {
        NSLog(@"Downloading file!");
       
        return NO;
    }
    return YES;
}