- 在
AppDelegate里面添加一个Reachability的实例属性。这里需要定义一个属性，而且这个属性需要在应用周期内存活，这样才可以对网络进行监听和发出通知。
-
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions方法里面开启网络监听。
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil];
NSString *remoteHostName =
self.hostReachability = [Reachability reachabilityWithHostName:remoteHostName];
[self.hostReachability startNotifier];
return YES;
}