iPhone判断是否接入网络
在这里介绍一种较为简单的判断是否连接网络的方法，首先要引入Reachability.h和.m文件，没有这两个文件的话，google之。然后在***AppDelegate.h中声明如下：

NetworkStatus remoteHostStatus;NetworkStatus internetConnectionStatus;NetworkStatus localWiFiConnectionStatus;...//Network@property NetworkStatus remoteHostStatus;@property NetworkStatus internetConnectionStatus;@property NetworkStatus localWiFiConnectionStatus;- (void) registerNetworkChecking;- (void) updateNetworkStatus;

- (void) registerNetworkChecking{[[Reachability sharedReachability] setHostName:@"www.baidu.com"];[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:@"kNetworkReachabilityChangedNotification"   object:nil];//[self updateNetworkStatus];}#pragma mark NetworkStatus Notification- (void)reachabilityChanged:(NSNotification *)note{//////NSLog(@"reachabilityChanged");    [self updateNetworkStatus];}- (void)updateNetworkStatus{// Query the SystemConfiguration framework for the state of the device's network connections.self.remoteHostStatus           = [[Reachability sharedReachability] remoteHostStatus];self.internetConnectionStatus= [[Reachability sharedReachability] internetConnectionStatus];self.localWiFiConnectionStatus= [[Reachability sharedReachability] localWiFiConnectionStatus];}

***AppDelegate *appDelegate = (***AppDelegate *)[[UIApplication sharedApplication] delegate];[appDelegate registerNetworkChecking];if (appDelegate.remoteHostStatus == NotReachable){      //未联网}else{      //联网}