NSData的dataWithContentsOfURL调用后为nil

                NSString *URL = [IMAGE_ADD_HEADER(urlStr) stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

                NSURL *url = [NSURL URLWithString:URL];

               UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:url]];//[NSData dataWithContentsOfURL:url]返回值为空；

//                NSData *data = UIImageJPEGRepresentation(image, 0.5);

有说在info.plist文件里添加Key：App Transport Security Settings —— Allow Arbitrary Loads 为YES 就可以了，但是这样设置了还是没好，所以换了个方式：

NSString *URL = [IMAGE_ADD_HEADER(urlStr) stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

                NSURL *url = [NSURL URLWithString:URL];

                NSData* data = [NSURLConnection sendSynchronousRequest:[NSURLRequest requestWithURL:url] returningResponse:NULL error:NULL];