谁能描述一下“NSURLErrorCancelled=-999”是如何使用的。 最佳答案 来自Apple文档:NSURLErrorCancelled(-999)"Returnedwhenanasynchronousloadiscanceled.AWebKitframeworkdelegatewillreceivethiserrorwhenitperformsacanceloperationonaloadingresource.NotethatanNSURLConnectionorNSURLDownloaddelegatewillno