//在向服务端发送请求状态栏显示网络活动标志:
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
//请求结束状态栏隐藏网络活动标志:
dispatch_async(dispatch_get_main_queue(), ^{
//状态栏隐藏活动
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
});