检查url字符串是否返回有效的网页。

How can I check if an image-url-string gives back a valid url? I'm talking about this url http://rscagen3t004-dev.tdlinx.dev/sites/all/themes/rsca/resources/images/RSCA_logo.png

如何检查image-url-string是否返回有效的URL？我在谈论这个网址http://rscagen3t004-dev.tdlinx.dev/sites/all/themes/rsca/resources/images/RSCA_logo.png

You can see when you click on the link that the webpage is not available. At the moment I'm doing this in my code:

您可以看到单击链接时网页不可用。目前我在我的代码中这样做：

 if([meta.met_thumb hasPrefix:@"http://"]){
                imgURL = meta.met_thumb;


                NSData *walImage = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:imgURL]];
                NSLog(@"walImage is %@",walImage);
                float newHeight2;
                if (walImage != nil) {
                    UIImage *imgIcon = [UIImage imageWithData:walImage];
                    if (imgIcon != nil) {
                        float width = imgIcon.size.width;
                        float heigt = imgIcon.size.height;
                        if(heigt < 240){
                            float newWidth = (heigt / 240);
                            float newWidht2 = (newWidth/ width);
                            //[imgNews setFrame:CGRectMake(40,y, newWidht2,heigt)];
                        }
                        float newHeight =  (width / 240);
                        newHeight2 = heigt/ newHeight;
                    }else{
                        newHeight2 = 240;
                    }

                }else{
                    newHeight2 = 240;
                }


                height = [self heightForStatus:attString] + y + newHeight2 + 70;
            }else{
                height = [self heightForStatus:attString] + y + 240 + 70;
            }

But it takes a very long time to execute the line of the [[NSData alloc] init].

但是执行[[NSData alloc] init]的行需要很长时间。

Can anybody help me with this?

任何人都可以帮我吗？

Thanks in advance !

提前致谢！

1 个解决方案

#1

The long delay in executing the line with alloc/init is probably caused by the slow response of the server. I just tested and after 30 seconds I neither got the image nor the error page.

使用alloc / init执行该行的长时间延迟可能是由于服务器响应缓慢造成的。我刚刚测试过，30秒后我既没有图像也没有错误页面。

To detect a "valid URL" you should check the server response. It should give a proper response of 404 = not found. Also see http response codes http://en.wikipedia.org/wiki/List_of_HTTP_status_codes

要检测“有效URL”，您应该检查服务器响应。它应该给出正确的响应404 =未找到。另请参阅http响应代码http://en.wikipedia.org/wiki/List_of_HTTP_status_codes

So what you should do is check wether you get a 404 or the according 2xx response. Then decide if you have data and create your image. Still, that may go wrong, if for example no image data is received but a web page.

那么你应该做的就是检查你得到404或2xx响应。然后决定是否有数据并创建图像。但是，如果例如没有接收到图像数据而是网页，则可能出错。

#1