iOS---检测网络状态

将Reachability.h 和 Reachability.m 加到自己的项目中，并引用 SystemConfiguration.framework，就可以使用了。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{if (([Reachability reachabilityForInternetConnection].currentReachabilityStatus==NotReachable)||([Reachability reachabilityForLocalWiFi].currentReachabilityStatus==NotReachable))    {        UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"警告" message:@"您的设备暂时没有可用的网络！" delegate:self cancelButtonTitle:@"确定" otherButtonTitles: nil];        [alert show];        [alert release];    } }