引入SystemConfiguration库并添加头文件：
#import <SystemConfiguration/SystemConfiguration.h>
代码如下：
NSArray *ifs = (__bridgeid)CNCopySupportedInterfaces();
for (NSString *ifnam in ifs) {
NSDictionary *info = (__bridgeid)CNCopyCurrentNetworkInfo((__bridgeCFStringRef)ifnam);
//info 保存了所有wifi联网的信息
if ([info allKeys] == nil) {
//wifi关闭了
}
}