iOS开发之监听网络连接，改变，断开

做iOS开发时，我们需要监控/监听网络状况，苹果提供了Reachability.h, Reachability.m。

导入Reachability.h

我们可以在 MainViewController的viewDidLoad方法内部写上：

1	[self checkReachability];

之后，具体方法如下

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#pragma mark #pragma mark Reachability Methods #pragma mark - (void)checkReachability {     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil];     self.reachability = [Reachability reachabilityForInternetConnection];     [self.reachability startNotifier];     [self updateInterfaceWithReachability:self.reachability]; } /*!  * Called by Reachability whenever status changes.  */ - (void) reachabilityChanged:(NSNotification *)note {     Reachability* curReach = [note object];     NSParameterAssert([curReach isKindOfClass:[Reachability class]]);     [self updateInterfaceWithReachability:curReach]; } - (void)updateInterfaceWithReachability:(Reachability *)reachability {     NetworkStatus status = [reachability currentReachabilityStatus];     AppDelegate *appDelegate = ((AppDelegate *) [[UIApplication sharedApplication] delegate]);     if(status == NotReachable)     {         //No internet         NSLog(@"No Internet");         appDelegate.isNetworkReachable = NO;         [_reachabilityImage setImage:[UIImage imageNamed:@"stop-32.png"]];     }     else if (status == ReachableViaWiFi)     {         //WiFi         NSLog(@"Reachable WIFI");         appDelegate.isNetworkReachable = YES;         [_reachabilityImage setImage:[UIImage imageNamed:@"Airport.png"]];     }     else if (status == ReachableViaWWAN)     {         //3G         NSLog(@"Reachable 3G");         appDelegate.isNetworkReachable = YES;         [_reachabilityImage setImage:[UIImage imageNamed:@"WWAN5.png"]];     } }