ios默认webview是有缓存的，所以不改变URL的话，刷新不了网页数据，或者像我这样写
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
if ([AFNetworkReachabilityManager sharedManager].reachable)
{
request.cachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
}
[self.webView loadRequest:request];